21731894784 has 640 divisors, whose sum is σ = 74480947200. Its totient is φ = 6210846720.

The previous prime is 21731894773. The next prime is 21731894791. The reversal of 21731894784 is 48749813712.

21731894784 is a `hidden beast` number, since 21 + 73 + 1 + 89 + 478 + 4 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a self number, because there is not a number n which added to its sum of digits gives 21731894784.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 138419634 + ... + 138419790.

It is an arithmetic number, because the mean of its divisors is an integer number (116376480).

Almost surely, 2^21731894784 is an apocalyptic number.

21731894784 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21731894784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37240473600).

21731894784 is an abundant number, since it is smaller than the sum of its proper divisors (52749052416).

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

21731894784 is a wasteful number, since it uses less digits than its factorization.

21731894784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 251 (or 229 counting only the distinct ones).

The product of its digits is 2709504, while the sum is 54.

The spelling of 21731894784 in words is "twenty-one billion, seven hundred thirty-one million, eight hundred ninety-four thousand, seven hundred eighty-four".