21337473721 has 6 divisors (see below), whose sum is σ = 22666451630. Its totient is φ = 20082327936.

The previous prime is 21337473709. The next prime is 21337473739. The reversal of 21337473721 is 12737473312.

It can be written as a sum of positive squares in 3 ways, for example, as 3009729321 + 18327744400 = 54861^2 + 135380^2 .

It is not a de Polignac number, because 21337473721 - 2²⁵ = 21303919289 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21337473791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36915756 + ... + 36916333.

Almost surely, 2^21337473721 is an apocalyptic number.

It is an amenable number.

21337473721 is a deficient number, since it is larger than the sum of its proper divisors (1328977909).

21337473721 is an equidigital number, since it uses as much as digits as its factorization.

21337473721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73832123 (or 73832106 counting only the distinct ones).

The product of its digits is 148176, while the sum is 40.

The spelling of 21337473721 in words is "twenty-one billion, three hundred thirty-seven million, four hundred seventy-three thousand, seven hundred twenty-one".