21981525 has 12 divisors (see below), whose sum is σ = 36342912. Its totient is φ = 11723440.

The previous prime is 21981497. The next prime is 21981559. The reversal of 21981525 is 52518912.

It is not a de Polignac number, because 21981525 - 2⁷ = 21981397 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 146469 + ... + 146618.

It is an arithmetic number, because the mean of its divisors is an integer number (3028576).

Almost surely, 2^21981525 is an apocalyptic number.

21981525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21981525 is a deficient number, since it is larger than the sum of its proper divisors (14361387).

21981525 is a wasteful number, since it uses less digits than its factorization.

21981525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 293100 (or 293095 counting only the distinct ones).

The product of its digits is 7200, while the sum is 33.

The square root of 21981525 is about 4688.4459045616. The cubic root of 21981525 is about 280.1254752255.

The spelling of 21981525 in words is "twenty-one million, nine hundred eighty-one thousand, five hundred twenty-five".