21165716057105 has 4 divisors (see below), whose sum is σ = 25398859268532. Its totient is φ = 16932572845680.

The previous prime is 21165716057089. The next prime is 21165716057113. The reversal of 21165716057105 is 50175061756112.

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 15748706519296 + 5417009537809 = 3968464^2 + 2327447^2 .

It is not a de Polignac number, because 21165716057105 - 2⁴ = 21165716057089 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21165716057105.

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, 2116571605706 + ... + 2116571605715.

It is an arithmetic number, because the mean of its divisors is an integer number (6349714817133).

Almost surely, 2^{21165716057105} is an apocalyptic number.

It is an amenable number.

21165716057105 is a deficient number, since it is larger than the sum of its proper divisors (4233143211427).

21165716057105 is an equidigital number, since it uses as much as digits as its factorization.

21165716057105 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4233143211426.

The product of its (nonzero) digits is 441000, while the sum is 47.

The spelling of 21165716057105 in words is "twenty-one trillion, one hundred sixty-five billion, seven hundred sixteen million, fifty-seven thousand, one hundred five".