21590915 has 4 divisors (see below), whose sum is σ = 25909104. Its totient is φ = 17272728.

The previous prime is 21590909. The next prime is 21590923. The reversal of 21590915 is 51909512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21590915 - 2⁸ = 21590659 is a prime.

It is a super-2 number, since 2×21590915² = 932335221074450, which contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2159087 + ... + 2159096.

It is an arithmetic number, because the mean of its divisors is an integer number (6477276).

Almost surely, 2^21590915 is an apocalyptic number.

21590915 is a deficient number, since it is larger than the sum of its proper divisors (4318189).

21590915 is an equidigital number, since it uses as much as digits as its factorization.

21590915 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4318188.

The product of its (nonzero) digits is 4050, while the sum is 32.

The square root of 21590915 is about 4646.6025222737. The cubic root of 21590915 is about 278.4562793241.

The spelling of 21590915 in words is "twenty-one million, five hundred ninety thousand, nine hundred fifteen".