21256476784 has 40 divisors (see below), whose sum is σ = 43602722640. Its totient is φ = 10010631168.

The previous prime is 21256476701. The next prime is 21256476823. The reversal of 21256476784 is 48767465212.

It is a Smith number, since the sum of its digits (52) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 149497 + ... + 254680.

It is an arithmetic number, because the mean of its divisors is an integer number (1090068066).

Almost surely, 2^21256476784 is an apocalyptic number.

It is an amenable number.

21256476784 is an abundant number, since it is smaller than the sum of its proper divisors (22346245856).

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

21256476784 is a wasteful number, since it uses less digits than its factorization.

21256476784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 404377 (or 404371 counting only the distinct ones).

The product of its digits is 4515840, while the sum is 52.

The spelling of 21256476784 in words is "twenty-one billion, two hundred fifty-six million, four hundred seventy-six thousand, seven hundred eighty-four".