21709642065 has 64 divisors (see below), whose sum is σ = 36361543680. Its totient is φ = 11050698240.

The previous prime is 21709642037. The next prime is 21709642069. The reversal of 21709642065 is 56024690712.

It is not a de Polignac number, because 21709642065 - 2⁸ = 21709641809 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21709642069) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 8090214 + ... + 8092896.

It is an arithmetic number, because the mean of its divisors is an integer number (568149120).

Almost surely, 2^21709642065 is an apocalyptic number.

It is an amenable number.

21709642065 is a deficient number, since it is larger than the sum of its proper divisors (14651901615).

21709642065 is a wasteful number, since it uses less digits than its factorization.

21709642065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3014.

The product of its (nonzero) digits is 181440, while the sum is 42.

The spelling of 21709642065 in words is "twenty-one billion, seven hundred nine million, six hundred forty-two thousand, sixty-five".