21171956780 has 48 divisors (see below), whose sum is σ = 49962999744. Its totient is φ = 7477451520.

The previous prime is 21171956779. The next prime is 21171956801. The reversal of 21171956780 is 8765917112.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1764251 + ... + 1776210.

It is an arithmetic number, because the mean of its divisors is an integer number (1040895828).

Almost surely, 2^21171956780 is an apocalyptic number.

21171956780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21171956780 is an abundant number, since it is smaller than the sum of its proper divisors (28791042964).

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

21171956780 is a wasteful number, since it uses less digits than its factorization.

21171956780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3540506 (or 3540504 counting only the distinct ones).

The product of its (nonzero) digits is 211680, while the sum is 47.

The spelling of 21171956780 in words is "twenty-one billion, one hundred seventy-one million, nine hundred fifty-six thousand, seven hundred eighty".