21597372 has 18 divisors (see below), whose sum is σ = 54593448. Its totient is φ = 7199112.

The previous prime is 21597353. The next prime is 21597377. The reversal of 21597372 is 27379512.

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 599927 = 21597372 / (2 + 1 + 5 + 9 + 7 + 3 + 7 + 2).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21597377) 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, 299928 + ... + 299999.

Almost surely, 2^21597372 is an apocalyptic number.

It is an amenable number.

21597372 is an abundant number, since it is smaller than the sum of its proper divisors (32996076).

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

21597372 is a wasteful number, since it uses less digits than its factorization.

21597372 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 599937 (or 599932 counting only the distinct ones).

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

The square root of 21597372 is about 4647.2972790645. The cubic root of 21597372 is about 278.4840350259.

The spelling of 21597372 in words is "twenty-one million, five hundred ninety-seven thousand, three hundred seventy-two".