21525537 has 24 divisors (see below), whose sum is σ = 33218080. Its totient is φ = 12355200.

The previous prime is 21525529. The next prime is 21525541. The reversal of 21525537 is 73552512.

It is not a de Polignac number, because 21525537 - 2³ = 21525529 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21525547) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5337 + ... + 8457.

Almost surely, 2^21525537 is an apocalyptic number.

It is an amenable number.

21525537 is a deficient number, since it is larger than the sum of its proper divisors (11692543).

21525537 is a wasteful number, since it uses less digits than its factorization.

21525537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3165 (or 3154 counting only the distinct ones).

The product of its digits is 10500, while the sum is 30.

The square root of 21525537 is about 4639.5621560660. The cubic root of 21525537 is about 278.1749369072.

It can be divided in two parts, 215 and 25537, that added together give a palindrome (25752).

The spelling of 21525537 in words is "twenty-one million, five hundred twenty-five thousand, five hundred thirty-seven".