21642103565 has 4 divisors (see below), whose sum is σ = 25970524284. Its totient is φ = 17313682848.

The previous prime is 21642103531. The next prime is 21642103579. The reversal of 21642103565 is 56530124612.

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 6073552489 + 15568551076 = 77933^2 + 124774^2 .

It is a cyclic number.

It is not a de Polignac number, because 21642103565 - 2¹⁰ = 21642102541 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, 2164210352 + ... + 2164210361.

It is an arithmetic number, because the mean of its divisors is an integer number (6492631071).

Almost surely, 2^21642103565 is an apocalyptic number.

It is an amenable number.

21642103565 is a deficient number, since it is larger than the sum of its proper divisors (4328420719).

21642103565 is an equidigital number, since it uses as much as digits as its factorization.

21642103565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4328420718.

The product of its (nonzero) digits is 43200, while the sum is 35.

The spelling of 21642103565 in words is "twenty-one billion, six hundred forty-two million, one hundred three thousand, five hundred sixty-five".