665557731 has 12 divisors (see below), whose sum is σ = 963902680. Its totient is φ = 442532160.

The previous prime is 665557723. The next prime is 665557747. The reversal of 665557731 is 137755566.

665557731 is a `hidden beast` number, since 6 + 65 + 557 + 7 + 31 = 666.

It is not a de Polignac number, because 665557731 - 2³ = 665557723 is a prime.

It is a super-2 number, since 2×665557731² = 885934186587736722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665557721) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 94150 + ... + 100971.

Almost surely, 2^665557731 is an apocalyptic number.

665557731 is a deficient number, since it is larger than the sum of its proper divisors (298344949).

665557731 is a wasteful number, since it uses less digits than its factorization.

665557731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 195506 (or 195503 counting only the distinct ones).

The product of its digits is 661500, while the sum is 45.

The square root of 665557731 is about 25798.4055902686. The cubic root of 665557731 is about 873.0958236515.

The spelling of 665557731 in words is "six hundred sixty-five million, five hundred fifty-seven thousand, seven hundred thirty-one".