21122112578 has 54 divisors (see below), whose sum is σ = 37700548011. Its totient is φ = 8849471904.

The previous prime is 21122112551. The next prime is 21122112581. The reversal of 21122112578 is 87521122112.

It can be written as a sum of positive squares in 5 ways, for example, as 7877095009 + 13245017569 = 88753^2 + 115087^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=102767.

It is a super-2 number, since 2×21122112578² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 76252976 + ... + 76253252.

Almost surely, 2^21122112578 is an apocalyptic number.

21122112578 is a deficient number, since it is larger than the sum of its proper divisors (16578435433).

21122112578 is an frugal number, since it uses more digits than its factorization.

21122112578 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 676 (or 339 counting only the distinct ones).

The product of its digits is 4480, while the sum is 32.

Multiplying 21122112578 by its sum of digits (32), we get a square (675907602496 = 822136²).

The spelling of 21122112578 in words is "twenty-one billion, one hundred twenty-two million, one hundred twelve thousand, five hundred seventy-eight".