21756103315561 has 4 divisors (see below), whose sum is σ = 21756175416400. Its totient is φ = 21756031214724.

The previous prime is 21756103315547. The next prime is 21756103315619. The reversal of 21756103315561 is 16551330165712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21756103315561 - 2²⁷ = 21755969097833 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21756103115561) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 35595891 + ... + 36201928.

It is an arithmetic number, because the mean of its divisors is an integer number (5439043854100).

Almost surely, 2^{21756103315561} is an apocalyptic number.

It is an amenable number.

21756103315561 is a deficient number, since it is larger than the sum of its proper divisors (72100839).

21756103315561 is an equidigital number, since it uses as much as digits as its factorization.

21756103315561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72100838.

The product of its (nonzero) digits is 567000, while the sum is 46.

The spelling of 21756103315561 in words is "twenty-one trillion, seven hundred fifty-six billion, one hundred three million, three hundred fifteen thousand, five hundred sixty-one".