21988680 has 64 divisors (see below), whose sum is σ = 75392640. Its totient is φ = 5025792.

The previous prime is 21988657. The next prime is 21988697. The reversal of 21988680 is 8688912.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12249 + ... + 13928.

It is an arithmetic number, because the mean of its divisors is an integer number (1178010).

Almost surely, 2^21988680 is an apocalyptic number.

21988680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21988680 is an abundant number, since it is smaller than the sum of its proper divisors (53403960).

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

21988680 is a wasteful number, since it uses less digits than its factorization.

21988680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26198 (or 26194 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 42.

The square root of 21988680 is about 4689.2088885013. The cubic root of 21988680 is about 280.1558656003.

It can be divided in two parts, 2198 and 8680, that added together give a triangular number (10878 = T₁₄₇).

The spelling of 21988680 in words is "twenty-one million, nine hundred eighty-eight thousand, six hundred eighty".