21681880 has 32 divisors (see below), whose sum is σ = 53220240. Its totient is φ = 7884160.

The previous prime is 21681871. The next prime is 21681883. The reversal of 21681880 is 8818612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21681883) by changing a digit.

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, 24199 + ... + 25078.

Almost surely, 2^21681880 is an apocalyptic number.

21681880 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21681880 is an abundant number, since it is smaller than the sum of its proper divisors (31538360).

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

21681880 is a wasteful number, since it uses less digits than its factorization.

21681880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49299 (or 49295 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 34.

The square root of 21681880 is about 4656.3805686391. The cubic root of 21681880 is about 278.8467874933.

The spelling of 21681880 in words is "twenty-one million, six hundred eighty-one thousand, eight hundred eighty".