21591224864 has 96 divisors (see below), whose sum is σ = 49097482560. Its totient is φ = 9243417600.

The previous prime is 21591224843. The next prime is 21591224869. The reversal of 21591224864 is 46842219512.

It is a super-2 number, since 2×21591224864² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is not an unprimeable number, because it can be changed into a prime (21591224869) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 1147694 + ... + 1166354.

It is an arithmetic number, because the mean of its divisors is an integer number (511432110).

Almost surely, 2^21591224864 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21591224864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24548741280).

21591224864 is an abundant number, since it is smaller than the sum of its proper divisors (27506257696).

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

21591224864 is a wasteful number, since it uses less digits than its factorization.

21591224864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18874 (or 18866 counting only the distinct ones).

The product of its digits is 276480, while the sum is 44.

The spelling of 21591224864 in words is "twenty-one billion, five hundred ninety-one million, two hundred twenty-four thousand, eight hundred sixty-four".