21025990 has 16 divisors (see below), whose sum is σ = 38870352. Its totient is φ = 8182944.

The previous prime is 21025987. The next prime is 21026053. The reversal of 21025990 is 9952012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28044 + ... + 28783.

It is an arithmetic number, because the mean of its divisors is an integer number (2429397).

Almost surely, 2^21025990 is an apocalyptic number.

21025990 is a deficient number, since it is larger than the sum of its proper divisors (17844362).

21025990 is a wasteful number, since it uses less digits than its factorization.

21025990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56871.

The product of its (nonzero) digits is 1620, while the sum is 28.

The square root of 21025990 is about 4585.4105595901. The cubic root of 21025990 is about 276.0061872869.

Subtracting from 21025990 its product of nonzero digits (1620), we obtain a triangular number (21024370 = T₆₄₈₄).

The spelling of 21025990 in words is "twenty-one million, twenty-five thousand, nine hundred ninety".