21221366536 has 16 divisors (see below), whose sum is σ = 40715413200. Its totient is φ = 10363923024.

The previous prime is 21221366533. The next prime is 21221366591. The reversal of 21221366536 is 63566312212.

It is a junction number, because it is equal to n+sod(n) for n = 21221366495 and 21221366504.

It is not an unprimeable number, because it can be changed into a prime (21221366533) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30844666 + ... + 30845353.

It is an arithmetic number, because the mean of its divisors is an integer number (2544713325).

Almost surely, 2^21221366536 is an apocalyptic number.

It is an amenable number.

21221366536 is a deficient number, since it is larger than the sum of its proper divisors (19494046664).

21221366536 is a wasteful number, since it uses less digits than its factorization.

21221366536 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61690068 (or 61690064 counting only the distinct ones).

The product of its digits is 77760, while the sum is 37.

Adding to 21221366536 its reverse (63566312212), we get a palindrome (84787678748).

The spelling of 21221366536 in words is "twenty-one billion, two hundred twenty-one million, three hundred sixty-six thousand, five hundred thirty-six".