21591229578 has 32 divisors (see below), whose sum is σ = 43278230016. Its totient is φ = 7181135808.

The previous prime is 21591229573. The next prime is 21591229607. The reversal of 21591229578 is 87592219512.

It is a self number, because there is not a number n which added to its sum of digits gives 21591229578.

It is not an unprimeable number, because it can be changed into a prime (21591229571) 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, 7107876 + ... + 7110912.

It is an arithmetic number, because the mean of its divisors is an integer number (1352444688).

Almost surely, 2^21591229578 is an apocalyptic number.

21591229578 is an abundant number, since it is smaller than the sum of its proper divisors (21687000438).

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

21591229578 is a wasteful number, since it uses less digits than its factorization.

21591229578 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5278.

The product of its digits is 907200, while the sum is 51.

The spelling of 21591229578 in words is "twenty-one billion, five hundred ninety-one million, two hundred twenty-nine thousand, five hundred seventy-eight".