21565981228 has 24 divisors (see below), whose sum is σ = 41356062720. Its totient is φ = 9758755920.

The previous prime is 21565981121. The next prime is 21565981247. The reversal of 21565981228 is 82218956512.

It is a hoax number, since the sum of its digits (49) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1089148 + ... + 1108771.

It is an arithmetic number, because the mean of its divisors is an integer number (1723169280).

Almost surely, 2^21565981228 is an apocalyptic number.

It is an amenable number.

21565981228 is a deficient number, since it is larger than the sum of its proper divisors (19790081492).

21565981228 is a wasteful number, since it uses less digits than its factorization.

21565981228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2198157 (or 2198155 counting only the distinct ones).

The product of its digits is 691200, while the sum is 49.

The spelling of 21565981228 in words is "twenty-one billion, five hundred sixty-five million, nine hundred eighty-one thousand, two hundred twenty-eight".