21721561080 has 64 divisors (see below), whose sum is σ = 66082521600. Its totient is φ = 5710830720.

The previous prime is 21721561039. The next prime is 21721561087. The reversal of 21721561080 is 8016512712.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21721561087) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1266220 + ... + 1283259.

It is an arithmetic number, because the mean of its divisors is an integer number (1032539400).

Almost surely, 2^21721561080 is an apocalyptic number.

21721561080 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21721561080 is an abundant number, since it is smaller than the sum of its proper divisors (44360960520).

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

21721561080 is a wasteful number, since it uses less digits than its factorization.

21721561080 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2549564 (or 2549560 counting only the distinct ones).

The product of its (nonzero) digits is 6720, while the sum is 33.

The spelling of 21721561080 in words is "twenty-one billion, seven hundred twenty-one million, five hundred sixty-one thousand, eighty".