21550312765 has 4 divisors (see below), whose sum is σ = 25860375324. Its totient is φ = 17240250208.

The previous prime is 21550312739. The next prime is 21550312789. The reversal of 21550312765 is 56721305512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6492814084 + 15057498681 = 80578^2 + 122709^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21550312765 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2155031272 + ... + 2155031281.

It is an arithmetic number, because the mean of its divisors is an integer number (6465093831).

Almost surely, 2^21550312765 is an apocalyptic number.

It is an amenable number.

21550312765 is a deficient number, since it is larger than the sum of its proper divisors (4310062559).

21550312765 is an equidigital number, since it uses as much as digits as its factorization.

21550312765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4310062558.

The product of its (nonzero) digits is 63000, while the sum is 37.

The spelling of 21550312765 in words is "twenty-one billion, five hundred fifty million, three hundred twelve thousand, seven hundred sixty-five".