21028972 has 18 divisors (see below), whose sum is σ = 38842188. Its totient is φ = 9960408.

The previous prime is 21028939. The next prime is 21028979. The reversal of 21028972 is 27982012.

It is a hoax number, since the sum of its digits (31) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21028979) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 5838 + ... + 8725.

Almost surely, 2^21028972 is an apocalyptic number.

It is an amenable number.

21028972 is a deficient number, since it is larger than the sum of its proper divisors (17813216).

21028972 is a wasteful number, since it uses less digits than its factorization.

21028972 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14605 (or 14584 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 21028972 is about 4585.7357097853. The cubic root of 21028972 is about 276.0192348143.

The spelling of 21028972 in words is "twenty-one million, twenty-eight thousand, nine hundred seventy-two".