21465564685 has 4 divisors (see below), whose sum is σ = 25758677628. Its totient is φ = 17172451744.

The previous prime is 21465564649. The next prime is 21465564707. The reversal of 21465564685 is 58646556412.

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 15321983524 + 6143581161 = 123782^2 + 78381^2 .

It is a cyclic number.

It is not a de Polignac number, because 21465564685 - 2⁹ = 21465564173 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2146556464 + ... + 2146556473.

It is an arithmetic number, because the mean of its divisors is an integer number (6439669407).

Almost surely, 2^21465564685 is an apocalyptic number.

It is an amenable number.

21465564685 is a deficient number, since it is larger than the sum of its proper divisors (4293112943).

21465564685 is an equidigital number, since it uses as much as digits as its factorization.

21465564685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4293112942.

The product of its digits is 6912000, while the sum is 52.

The spelling of 21465564685 in words is "twenty-one billion, four hundred sixty-five million, five hundred sixty-four thousand, six hundred eighty-five".