21573972 has 48 divisors (see below), whose sum is σ = 63925120. Its totient is φ = 6163776.

The previous prime is 21573971. The next prime is 21573973. The reversal of 21573972 is 27937512.

It is an interprime number because it is at equal distance from previous prime (21573971) and next prime (21573973).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21573971) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13513 + ... + 15024.

Almost surely, 2^21573972 is an apocalyptic number.

It is an amenable number.

21573972 is an abundant number, since it is smaller than the sum of its proper divisors (42351148).

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

21573972 is a wasteful number, since it uses less digits than its factorization.

21573972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28557 (or 28549 counting only the distinct ones).

The product of its digits is 26460, while the sum is 36.

The square root of 21573972 is about 4644.7790044307. The cubic root of 21573972 is about 278.3834227644.

The spelling of 21573972 in words is "twenty-one million, five hundred seventy-three thousand, nine hundred seventy-two".