21521680 has 40 divisors (see below), whose sum is σ = 52675200. Its totient is φ = 8155008.

The previous prime is 21521671. The next prime is 21521693. The reversal of 21521680 is 8612512.

It is a tau number, because it is divible by the number of its divisors (40).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5560 + ... + 8599.

It is an arithmetic number, because the mean of its divisors is an integer number (1316880).

Almost surely, 2^21521680 is an apocalyptic number.

21521680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21521680 is an abundant number, since it is smaller than the sum of its proper divisors (31153520).

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

21521680 is a wasteful number, since it uses less digits than its factorization.

21521680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14191 (or 14185 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 21521680 is about 4639.1464732211. The cubic root of 21521680 is about 278.1583212192.

It can be divided in two parts, 215216 and 80, that added together give a square (215296 = 464²).

The spelling of 21521680 in words is "twenty-one million, five hundred twenty-one thousand, six hundred eighty".