21521508 has 12 divisors (see below), whose sum is σ = 50216880. Its totient is φ = 7173832.

The previous prime is 21521503. The next prime is 21521527. The reversal of 21521508 is 80512512.

It is a tau number, because it is divible by the number of its divisors (12).

It is not an unprimeable number, because it can be changed into a prime (21521503) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 896718 + ... + 896741.

It is an arithmetic number, because the mean of its divisors is an integer number (4184740).

Almost surely, 2^21521508 is an apocalyptic number.

It is an amenable number.

21521508 is an abundant number, since it is smaller than the sum of its proper divisors (28695372).

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

21521508 is a wasteful number, since it uses less digits than its factorization.

21521508 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1793466 (or 1793464 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 24.

The square root of 21521508 is about 4639.1279352913. The cubic root of 21521508 is about 278.1575802089.

The spelling of 21521508 in words is "twenty-one million, five hundred twenty-one thousand, five hundred eight".