661665231 has 12 divisors (see below), whose sum is σ = 971407320. Its totient is φ = 433878480.

The previous prime is 661665223. The next prime is 661665233. The reversal of 661665231 is 132566166.

661665231 is a `hidden beast` number, since 6 + 616 + 6 + 5 + 2 + 31 = 666.

It is not a de Polignac number, because 661665231 - 2³ = 661665223 is a prime.

It is a super-2 number, since 2×661665231² = 875601755828566722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661665233) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 602061 + ... + 603158.

It is an arithmetic number, because the mean of its divisors is an integer number (80950610).

Almost surely, 2^661665231 is an apocalyptic number.

661665231 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

661665231 is a deficient number, since it is larger than the sum of its proper divisors (309742089).

661665231 is a wasteful number, since it uses less digits than its factorization.

661665231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1205286 (or 1205283 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The square root of 661665231 is about 25722.8542545340. The cubic root of 661665231 is about 871.3904005919.

The spelling of 661665231 in words is "six hundred sixty-one million, six hundred sixty-five thousand, two hundred thirty-one".