21905715 has 16 divisors (see below), whose sum is σ = 37745568. Its totient is φ = 10784256.

The previous prime is 21905711. The next prime is 21905749. The reversal of 21905715 is 51750912.

It is not a de Polignac number, because 21905715 - 2² = 21905711 is a prime.

It is a super-2 number, since 2×21905715² = 959720699322450, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21905711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 55974 + ... + 56363.

It is an arithmetic number, because the mean of its divisors is an integer number (2359098).

Almost surely, 2^21905715 is an apocalyptic number.

21905715 is a deficient number, since it is larger than the sum of its proper divisors (15839853).

21905715 is a wasteful number, since it uses less digits than its factorization.

21905715 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 112358.

The product of its (nonzero) digits is 3150, while the sum is 30.

The square root of 21905715 is about 4680.3541532666. The cubic root of 21905715 is about 279.8030715636.

The spelling of 21905715 in words is "twenty-one million, nine hundred five thousand, seven hundred fifteen".