21820555988 has 48 divisors (see below), whose sum is σ = 48415449600. Its totient is φ = 8357414880.

The previous prime is 21820555979. The next prime is 21820555997. The reversal of 21820555988 is 88955502812.

It is an interprime number because it is at equal distance from previous prime (21820555979) and next prime (21820555997).

It is a super-2 number, since 2×21820555988² (a number of 21 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (53) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 582218 + ... + 618561.

It is an arithmetic number, because the mean of its divisors is an integer number (1008655200).

Almost surely, 2^21820555988 is an apocalyptic number.

21820555988 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21820555988 is an abundant number, since it is smaller than the sum of its proper divisors (26594893612).

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

21820555988 is a wasteful number, since it uses less digits than its factorization.

21820555988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1200860 (or 1200858 counting only the distinct ones).

The product of its (nonzero) digits is 2304000, while the sum is 53.

The spelling of 21820555988 in words is "twenty-one billion, eight hundred twenty million, five hundred fifty-five thousand, nine hundred eighty-eight".