21715951 has 2 divisors, whose sum is σ = 21715952. Its totient is φ = 21715950.

The previous prime is 21715931. The next prime is 21715997. The reversal of 21715951 is 15951712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21715951 - 2⁷ = 21715823 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21715921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10857975 + 10857976.

It is an arithmetic number, because the mean of its divisors is an integer number (10857976).

Almost surely, 2^21715951 is an apocalyptic number.

21715951 is a deficient number, since it is larger than the sum of its proper divisors (1).

21715951 is an equidigital number, since it uses as much as digits as its factorization.

21715951 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3150, while the sum is 31.

The square root of 21715951 is about 4660.0376607920. The cubic root of 21715951 is about 278.9927714027.

The spelling of 21715951 in words is "twenty-one million, seven hundred fifteen thousand, nine hundred fifty-one".