# 21

3

4

32

21 = 3 × 7

Factor Count
3 1
7 1

441

9261

## Square root of 21

4.58257569495583982899233888019808...

## Cube root of 21

2.75892417638112030786601280851755...

231

## Reciprocal of 21

0.0476190476190476

10101

5

## Octal of 21

25

15

 Prime number No Hexagonal number No Perfect number No Deficient number No Abundant number No Mersenne number No Harshad number Yes Harmonic divisor number No

QR21 (sequence)

33

12

6

1

## Properties of 21

Properties of the number 21: 21 has 4 divisors. The divisors of 21 are 1, 3, 7, 21 and the sum of them is 32. The factorization of 21 is 3 × 7. The square and cube of 21 are 441 and 9261 respectively. The square root and cube root of 21 are 4.58257569495583982899233888019808... and 2.75892417638112030786601280851755.... The binary, octal, hexadecimal of 21 are 10101, 25, 15. 21 is not a prime number, not hexagonal number, not perfect number, not deficient number, not Mersenne number, not Mersenne number, Harshad number, not harmonic divisor number.

## sin 21

0.83665563853605595667772831802722...

## cos 21

-0.54772926022426848824409262306290...

## tan 21

-1.52749852763660309840076934051467...

## sin 21°

0.35836794954530026835470835067099...

## cos 21°

0.93358042649720174299687869279296...

## tan 21°

0.38386403503541577375557380946702...

## log 21

3.04452243772342301397770825133193...

## log10 21

1.32221929473391930365266944136238...

## log2 21

4.39231742277876069380226908833720...