665811131 has 16 divisors (see below), whose sum is σ = 685977600. Its totient is φ = 646053408.

The previous prime is 665811127. The next prime is 665811169. The reversal of 665811131 is 131118566.

It is a cyclic number.

It is not a de Polignac number, because 665811131 - 2² = 665811127 is a prime.

It is a super-2 number, since 2×665811131² = 886608924326998322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665811101) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1437806 + ... + 1438268.

It is an arithmetic number, because the mean of its divisors is an integer number (42873600).

Almost surely, 2^665811131 is an apocalyptic number.

665811131 is a deficient number, since it is larger than the sum of its proper divisors (20166469).

665811131 is a wasteful number, since it uses less digits than its factorization.

665811131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 818.

The product of its digits is 4320, while the sum is 32.

The square root of 665811131 is about 25803.3162791142. The cubic root of 665811131 is about 873.2066151472.

Adding to 665811131 its reverse (131118566), we get a palindrome (796929697).

The spelling of 665811131 in words is "six hundred sixty-five million, eight hundred eleven thousand, one hundred thirty-one".