21720322765 has 16 divisors (see below), whose sum is σ = 28050012720. Its totient is φ = 16086021120.

The previous prime is 21720322753. The next prime is 21720322781. The reversal of 21720322765 is 56722302712.

It can be written as a sum of positive squares in 8 ways, for example, as 4468996 + 21715853769 = 2114^2 + 147363^2 .

It is not a de Polignac number, because 21720322765 - 2²³ = 21711934157 is a prime.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 2089350 + ... + 2099719.

It is an arithmetic number, because the mean of its divisors is an integer number (1753125795).

Almost surely, 2^21720322765 is an apocalyptic number.

It is an amenable number.

21720322765 is a deficient number, since it is larger than the sum of its proper divisors (6329689955).

21720322765 is a wasteful number, since it uses less digits than its factorization.

21720322765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4189152.

The product of its (nonzero) digits is 70560, while the sum is 37.

The spelling of 21720322765 in words is "twenty-one billion, seven hundred twenty million, three hundred twenty-two thousand, seven hundred sixty-five".