21317915 has 8 divisors (see below), whose sum is σ = 27086400. Its totient is φ = 16051072.

The previous prime is 21317899. The next prime is 21317921. The reversal of 21317915 is 51971312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21317915 - 2⁴ = 21317899 is a prime.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 125315 + ... + 125484.

It is an arithmetic number, because the mean of its divisors is an integer number (3385800).

Almost surely, 2^21317915 is an apocalyptic number.

21317915 is a deficient number, since it is larger than the sum of its proper divisors (5768485).

21317915 is a wasteful number, since it uses less digits than its factorization.

21317915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 250821.

The product of its digits is 1890, while the sum is 29.

The square root of 21317915 is about 4617.1327682881. The cubic root of 21317915 is about 277.2776781669.

The spelling of 21317915 in words is "twenty-one million, three hundred seventeen thousand, nine hundred fifteen".