21666510065 has 32 divisors (see below), whose sum is σ = 28177632000. Its totient is φ = 15939348480.

The previous prime is 21666510053. The next prime is 21666510077. The reversal of 21666510065 is 56001566612.

It is an interprime number because it is at equal distance from previous prime (21666510053) and next prime (21666510077).

It is not a de Polignac number, because 21666510065 - 2¹⁰ = 21666509041 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 761129 + ... + 789081.

It is an arithmetic number, because the mean of its divisors is an integer number (880551000).

Almost surely, 2^21666510065 is an apocalyptic number.

It is an amenable number.

21666510065 is a deficient number, since it is larger than the sum of its proper divisors (6511121935).

21666510065 is a wasteful number, since it uses less digits than its factorization.

21666510065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28217.

The product of its (nonzero) digits is 64800, while the sum is 38.

The spelling of 21666510065 in words is "twenty-one billion, six hundred sixty-six million, five hundred ten thousand, sixty-five".