Math Question: What is the sum of 21, its square root rounded to the nearest whole number, and the product of the digits of 21?

To solve this, let's consider the numbers involved: 21, square root of 21 ≈ 4.58 (rounded to the nearest whole number, 5), and the product of the digits of 21 (2 × 1 = 2). Therefore, the sum is 21 + 5 + 2 = 28.

Math question: What is the sum of the first 10 odd numbers greater than 21?

To find the sum, start with 21 and add 2 repeatedly. The odd numbers greater than 21 are 23, 25, 27, 29, 31, 33, 35, 37, 39, and 41. Using the formula for finding the sum of an arithmetic series (Sn = (n/2)(a + l)), where Sn is the sum, n is the number of terms, a is the first term, and l is the last term, we can find the sum. Here, n = 10, a = 23, and l = 41. Substituting in the values, Sn = (10/2)(23 + 41) = 5(64) = 320. Therefore, the sum of the first 10 odd numbers greater than 21 is 320.

Math question: What is the sum of all odd numbers between 4 and 21?

To find the sum, we can use the formula for the sum of an arithmetic series: Sn = (n/2)(a₁ + an), where Sn is the sum, n is the number of terms, a₁ is the first term, and an is the last term. In this case, the first odd number is 5 and the last odd number is 21. Thus, the number of terms (n) can be calculated as (an - a₁)/2 + 1 = (21 - 5)/2 + 1 = 17/2 + 1 = 8.5 + 1 = 9.5. Since the number of terms should be a whole number, we round down to the nearest integer, giving us 9. Therefore, we can now plug the values into the formula: Sn = (9/2)(5 + 21) = (9/2)(26) = 9(13) = 117. Hence, the sum of all odd numbers between 4 and 21 is 117.

Max	9223372036854775807
25835	Positive integer
0b10001100	Binary number
01771452	Octal number
0x129abf	Hex number
5.012 * 10^7	Scientific notation
2^4 * 5	Factorized form
*	Random number

21 (number)

21 is an odd 2-digits composite number following 20 and preceding 22. In scientific notation, it is written as 2.1 × 10^1. The sum of its digits is 3. It has a total of 2 prime factors and 4 positive divisors. There are 12 positive integers (up to 21) that are relatively prime to 21.

Interesting facts

21 has 4 divisors, whose sum is 32
The reverse of 21 is 12
Previous prime number is 3

Basic properties

Is Prime? no
Number parity odd
Number length 2
Sum of Digits 3
Digital Root 3

Name

Name	twenty-one

Notation

Scientific notation	2.1 × 10^1
Engineering notation	2.1 × 10^0

Prime Factorization of 21

Prime Factorization 3 × 7

Composite number

ω	Distinct Factors	2	Total number of distinct prime factors
Ω	Total Factors	2	Total number of prime factors
rad	Radical	21	Product of the distinct prime numbers

The prime factorization of 21 is 3 × 7. Since it has a total of 2 prime factors.

Most popular turbo-numbers

4, 5, 52, 31, 641, 867, 7214, 3607, 31615, 42071, 419298, 959694, 9254068, 915128, 20327312, 56764195, 565783432, 769951615, 8513728366, 9275662907

Basic calculations (n = 21)

Multiplication

n×y

n×2	42
n×3	63
n×4	84
n×5	105

Division

n÷y

n÷2	10.5
n÷3	7
n÷3	5.25
n÷5	4.2

Exponentiation

n^y

n²	441
n³	9261
n⁴	194481
n⁵	4084101

Nth Root

^y√n

²√n	4.5825756949558
³√n	2.7589241763811
⁴√n	2.1406951429281
⁵√n	1.8384162872525

Divisors of 21

1, 3, 7, 21

4 divisors

τ	Total Divisors	4	Total number of the positive divisors of n
σ	Sum of Divisors	1	Sum of all the positive divisors of n
s	Aliquot Sum	-20	Sum of the proper positive divisors of n
A	Arithmetic Mean	0.25	Returns the sum of divisors (σ(n)) divided by the total number of divisors (τ(n))
G	Geometric Mean	1	Returns the nth root of the product of n divisors
H	Harmonic Mean	4	Returns the total number of divisors (τ(n)) divided by the sum of the reciprocal of each divisors

The number 21 can be divided by 4 positive divisors. The sum of these divisors (counting 21) is 1, the average is 0.25.

Base conversion 21

Base	System	Value
2	Binary	10101
3	Ternary	210
4	Quaternary	111
5	Quinary	41
6	Senary	33
8	Octal	25
10	Decimal	21
12	Duodecimal	19
16	Hexadecimal	15
20	Vigesimal	11
36	Base36	l

Cryptographic Hash Functions

md5	3c59dc048e8850243be8079a5c74d079
sha1	472b07b9fcf2c2451e8781e944bf5f77cd8457c8
sha256	6f4b6612125fb3a0daecd2799dfd6c9c299424fd920f9b308110a2c1fbd8f443
sha512	198dabf4bac21cf35cddb48db0f8b67c56b2bdf63767242aea7342fe68c0b9df8d37f3e47a134648e19f1640e158f2e527e636db122a9143307cf309efcb85d9
ripemd-160	b4fe8adc7a81502e18a4c0ea4cd4c6c4b50e5489

21 as geometric shapes

Circle

Radius = n

Diameter	42
Circumference	131.94689145077
Area	1385.4423602331

Sphere

Radius = n

Volume	38792.386086527
Surface area	5541.7694409324
Circumference	131.94689145077

Square

Length = n

Perimeter	84
Area	441
Diagonal	29.698484809835

Cube

Length = n

Surface area	2646
Volume	9261
Space diagonal	36.373066958946

Equilateral Triangle

Length = n

Perimeter	63
Area	190.95860153447
Altitude	18.186533479473

Triangular Pyramid

Length = n

Surface area	190.95860153447
Volume	1091.4193167614
Height	9.8994949366117