21525539 has 12 divisors (see below), whose sum is σ = 25721136. Its totient is φ = 17645232.

The previous prime is 21525529. The next prime is 21525541. The reversal of 21525539 is 93552512.

It is not a de Polignac number, because 21525539 - 2¹⁶ = 21460003 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21525529) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 797 + ... + 6609.

It is an arithmetic number, because the mean of its divisors is an integer number (2143428).

Almost surely, 2^21525539 is an apocalyptic number.

21525539 is a deficient number, since it is larger than the sum of its proper divisors (4195597).

21525539 is an equidigital number, since it uses as much as digits as its factorization.

21525539 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5866 (or 5843 counting only the distinct ones).

The product of its digits is 13500, while the sum is 32.

The square root of 21525539 is about 4639.5623716036. The cubic root of 21525539 is about 278.1749455226.

The spelling of 21525539 in words is "twenty-one million, five hundred twenty-five thousand, five hundred thirty-nine".