21525870 has 16 divisors (see below), whose sum is σ = 51662160. Its totient is φ = 5740224.

The previous prime is 21525857. The next prime is 21525883. The reversal of 21525870 is 7852512.

It is an interprime number because it is at equal distance from previous prime (21525857) and next prime (21525883).

It is a Harshad number since it is a multiple of its sum of digits (30), and also a Moran number because the ratio is a prime number: 717529 = 21525870 / (2 + 1 + 5 + 2 + 5 + 8 + 7 + 0).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 358735 + ... + 358794.

It is an arithmetic number, because the mean of its divisors is an integer number (3228885).

Almost surely, 2^21525870 is an apocalyptic number.

21525870 is an abundant number, since it is smaller than the sum of its proper divisors (30136290).

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

21525870 is a wasteful number, since it uses less digits than its factorization.

21525870 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 717539.

The product of its (nonzero) digits is 5600, while the sum is 30.

The square root of 21525870 is about 4639.5980429343. The cubic root of 21525870 is about 278.1763713550.

The spelling of 21525870 in words is "twenty-one million, five hundred twenty-five thousand, eight hundred seventy".