21221210538 has 24 divisors (see below), whose sum is σ = 50159225376. Its totient is φ = 6430669800.

The previous prime is 21221210533. The next prime is 21221210579. The reversal of 21221210538 is 83501212212.

21221210538 is a `hidden beast` number, since 2 + 1 + 2 + 2 + 121 + 0 + 538 = 666.

It is not an unprimeable number, because it can be changed into a prime (21221210533) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 53588718 + ... + 53589113.

It is an arithmetic number, because the mean of its divisors is an integer number (2089967724).

Almost surely, 2^21221210538 is an apocalyptic number.

21221210538 is an abundant number, since it is smaller than the sum of its proper divisors (28938014838).

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

21221210538 is a wasteful number, since it uses less digits than its factorization.

21221210538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107177850 (or 107177847 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The spelling of 21221210538 in words is "twenty-one billion, two hundred twenty-one million, two hundred ten thousand, five hundred thirty-eight".