Properties of the number

Number length
Sum of digits
Multiplication of digits
of 21 = 0.21
Parity
Odd
Is a prime number?
No
Next prime number
Is a composite number?
Yes
Is a semiprime number?
Yes
Is a linear number?
No
Is a square pyramidal number?
No
Triangular number
(T21)Is an abundant number?
No, it's a deficient number
Is a Fibonacci number?
Yes
Is a Harshad number?
(Niven number)Yes
Count of divisors
Sum of divisors
Multiplication of divisors
Factoring
(prime factors)3 × 7
Factorial
51090942171709440000
Inverse number
0.047619047619048
Exponentiation
2 441 3 9261 4 194481 5 4084101 6 85766121 7 1801088541 8 37822859361 9 794280046581 10 16679880978201
2√ 4.5825756949558 3√ 2.7589241763811 4√ 2.1406951429281 5√ 1.8384162872525 6√ 1.661000956165 7√ 1.5448576602502 8√ 1.4631114595027 9√ 1.4025335376029 10√ 1.3558821066938 1.3188692847805
Square root and remainder
42 + 5
Is a perfect square?
No
Is a perfect cube?
No
Natural logarithm
(loge)3.0445224377234
Common logarithm
(log10)1.3222192947339
Binary logarithm
(log2)4.3923174227788