21801660 has 24 divisors (see below), whose sum is σ = 61044816. Its totient is φ = 5813760.

The previous prime is 21801653. The next prime is 21801673. The reversal of 21801660 is 6610812.

It is a self number, because there is not a number n which added to its sum of digits gives 21801660.

It is a congruent number.

It is an unprimeable number.

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, 181621 + ... + 181740.

It is an arithmetic number, because the mean of its divisors is an integer number (2543534).

Almost surely, 2^21801660 is an apocalyptic number.

21801660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21801660 is an abundant number, since it is smaller than the sum of its proper divisors (39243156).

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

21801660 is a wasteful number, since it uses less digits than its factorization.

21801660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 363373 (or 363371 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 24.

The square root of 21801660 is about 4669.2247750563. The cubic root of 21801660 is about 279.3593345369.

The spelling of 21801660 in words is "twenty-one million, eight hundred one thousand, six hundred sixty".