21551646520 has 32 divisors (see below), whose sum is σ = 49406137920. Its totient is φ = 8458003840.

The previous prime is 21551646511. The next prime is 21551646533. The reversal of 21551646520 is 2564615512.

It is a super-2 number, since 2×21551646520² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21551646520.

It is a congruent number.

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, 5080816 + ... + 5085055.

It is an arithmetic number, because the mean of its divisors is an integer number (1543941810).

Almost surely, 2^21551646520 is an apocalyptic number.

21551646520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21551646520 is an abundant number, since it is smaller than the sum of its proper divisors (27854491400).

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

21551646520 is a wasteful number, since it uses less digits than its factorization.

21551646520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10165935 (or 10165931 counting only the distinct ones).

The product of its (nonzero) digits is 72000, while the sum is 37.

The spelling of 21551646520 in words is "twenty-one billion, five hundred fifty-one million, six hundred forty-six thousand, five hundred twenty".