11661566505 has 8 divisors (see below), whose sum is σ = 18658506432. Its totient is φ = 6219502128.

The previous prime is 11661566489. The next prime is 11661566509. The reversal of 11661566505 is 50566516611.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 11661566505 - 2⁴ = 11661566489 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (11661566509) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 388718869 + ... + 388718898.

It is an arithmetic number, because the mean of its divisors is an integer number (2332313304).

Almost surely, 2^11661566505 is an apocalyptic number.

11661566505 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

11661566505 is a deficient number, since it is larger than the sum of its proper divisors (6996939927).

11661566505 is an equidigital number, since it uses as much as digits as its factorization.

11661566505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 777437775.

The product of its (nonzero) digits is 162000, while the sum is 42.

The spelling of 11661566505 in words is "eleven billion, six hundred sixty-one million, five hundred sixty-six thousand, five hundred five".