21215790 has 32 divisors (see below), whose sum is σ = 56576160. Its totient is φ = 5657472.

The previous prime is 21215783. The next prime is 21215807. The reversal of 21215790 is 9751212.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 39019 + ... + 39558.

It is an arithmetic number, because the mean of its divisors is an integer number (1768005).

Almost surely, 2^21215790 is an apocalyptic number.

21215790 is an abundant number, since it is smaller than the sum of its proper divisors (35360370).

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

21215790 is a wasteful number, since it uses less digits than its factorization.

21215790 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78593 (or 78587 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 21215790 is about 4606.0601385566. The cubic root of 21215790 is about 276.8341963693.

The spelling of 21215790 in words is "twenty-one million, two hundred fifteen thousand, seven hundred ninety".