21551063820 has 96 divisors (see below), whose sum is σ = 70892478720. Its totient is φ = 4822613760.

The previous prime is 21551063813. The next prime is 21551063837. The reversal of 21551063820 is 2836015512.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1247310 + ... + 1264469.

It is an arithmetic number, because the mean of its divisors is an integer number (738463320).

Almost surely, 2^21551063820 is an apocalyptic number.

21551063820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21551063820 is an abundant number, since it is smaller than the sum of its proper divisors (49341414900).

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

21551063820 is a wasteful number, since it uses less digits than its factorization.

21551063820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2511815 (or 2511813 counting only the distinct ones).

The product of its (nonzero) digits is 14400, while the sum is 33.

The spelling of 21551063820 in words is "twenty-one billion, five hundred fifty-one million, sixty-three thousand, eight hundred twenty".