11651566661 has 4 divisors (see below), whose sum is σ = 13316076192. Its totient is φ = 9987057132.

The previous prime is 11651566657. The next prime is 11651566691. The reversal of 11651566661 is 16666515611.

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 11651566661 - 2² = 11651566657 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11651566601) 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, 832254755 + ... + 832254768.

It is an arithmetic number, because the mean of its divisors is an integer number (3329019048).

Almost surely, 2^11651566661 is an apocalyptic number.

It is an amenable number.

11651566661 is a deficient number, since it is larger than the sum of its proper divisors (1664509531).

11651566661 is an equidigital number, since it uses as much as digits as its factorization.

11651566661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1664509530.

The product of its digits is 194400, while the sum is 44.

The spelling of 11651566661 in words is "eleven billion, six hundred fifty-one million, five hundred sixty-six thousand, six hundred sixty-one".