21621572 has 24 divisors (see below), whose sum is σ = 43955520. Its totient is φ = 9113760.

The previous prime is 21621557. The next prime is 21621577. The reversal of 21621572 is 27512612.

It is not an unprimeable number, because it can be changed into a prime (21621577) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4622 + ... + 8037.

It is an arithmetic number, because the mean of its divisors is an integer number (1831480).

Almost surely, 2^21621572 is an apocalyptic number.

It is an amenable number.

21621572 is an abundant number, since it is smaller than the sum of its proper divisors (22333948).

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

21621572 is a wasteful number, since it uses less digits than its factorization.

21621572 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12731 (or 12729 counting only the distinct ones).

The product of its digits is 1680, while the sum is 26.

The square root of 21621572 is about 4649.9002139831. The cubic root of 21621572 is about 278.5880106093.

The spelling of 21621572 in words is "twenty-one million, six hundred twenty-one thousand, five hundred seventy-two".