21356433644 has 48 divisors (see below), whose sum is σ = 46405627968. Its totient is φ = 8373915648.

The previous prime is 21356433629. The next prime is 21356433661. The reversal of 21356433644 is 44633465312.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 218477 + ... + 300740.

It is an arithmetic number, because the mean of its divisors is an integer number (966783916).

Almost surely, 2^21356433644 is an apocalyptic number.

It is an amenable number.

21356433644 is an abundant number, since it is smaller than the sum of its proper divisors (25049194324).

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

21356433644 is a wasteful number, since it uses less digits than its factorization.

21356433644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 519354 (or 519352 counting only the distinct ones).

The product of its digits is 622080, while the sum is 41.

Adding to 21356433644 its reverse (44633465312), we get a palindrome (65989898956).

The spelling of 21356433644 in words is "twenty-one billion, three hundred fifty-six million, four hundred thirty-three thousand, six hundred forty-four".