21315690 has 64 divisors (see below), whose sum is σ = 62017920. Its totient is φ = 5166720.

The previous prime is 21315689. The next prime is 21315709. The reversal of 21315690 is 9651312.

It is a super-2 number, since 2×21315690² = 908717280352200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a zygodrome in base 3.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 619 + ... + 6558.

It is an arithmetic number, because the mean of its divisors is an integer number (969030).

Almost surely, 2^21315690 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21315690, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31008960).

21315690 is an abundant number, since it is smaller than the sum of its proper divisors (40702230).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21315690 is a wasteful number, since it uses less digits than its factorization.

21315690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7204 (or 7198 counting only the distinct ones).

The product of its (nonzero) digits is 1620, while the sum is 27.

The square root of 21315690 is about 4616.8918115979. The cubic root of 21315690 is about 277.2680311275.

The spelling of 21315690 in words is "twenty-one million, three hundred fifteen thousand, six hundred ninety".