21687980 has 24 divisors (see below), whose sum is σ = 45841488. Its totient is φ = 8618688.

The previous prime is 21687959. The next prime is 21687997. The reversal of 21687980 is 8978612.

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, 314 + ... + 6593.

It is an arithmetic number, because the mean of its divisors is an integer number (1910062).

Almost surely, 2^21687980 is an apocalyptic number.

21687980 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21687980 is an abundant number, since it is smaller than the sum of its proper divisors (24153508).

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

21687980 is a wasteful number, since it uses less digits than its factorization.

21687980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7073 (or 7071 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 41.

The square root of 21687980 is about 4657.0355377643. The cubic root of 21687980 is about 278.8729353783.

The spelling of 21687980 in words is "twenty-one million, six hundred eighty-seven thousand, nine hundred eighty".