21521394684 has 48 divisors (see below), whose sum is σ = 55819428000. Its totient is φ = 7170812928.

The previous prime is 21521394649. The next prime is 21521394701. The reversal of 21521394684 is 48649312512.

21521394684 is a `hidden beast` number, since 2 + 1 + 52 + 139 + 468 + 4 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 227292 + ... + 307740.

It is an arithmetic number, because the mean of its divisors is an integer number (1162904750).

Almost surely, 2^21521394684 is an apocalyptic number.

It is an amenable number.

21521394684 is an abundant number, since it is smaller than the sum of its proper divisors (34298033316).

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

21521394684 is a wasteful number, since it uses less digits than its factorization.

21521394684 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82939 (or 82931 counting only the distinct ones).

The product of its digits is 414720, while the sum is 45.

The spelling of 21521394684 in words is "twenty-one billion, five hundred twenty-one million, three hundred ninety-four thousand, six hundred eighty-four".