665117981 has 4 divisors (see below), whose sum is σ = 725583264. Its totient is φ = 604652700.

The previous prime is 665117977. The next prime is 665118017. The reversal of 665117981 is 189711566.

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 665117981 - 2² = 665117977 is a prime.

It is a super-2 number, since 2×665117981² = 884763857299032722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665117081) 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, 30232625 + ... + 30232646.

It is an arithmetic number, because the mean of its divisors is an integer number (181395816).

Almost surely, 2^665117981 is an apocalyptic number.

It is an amenable number.

665117981 is a deficient number, since it is larger than the sum of its proper divisors (60465283).

665117981 is a wasteful number, since it uses less digits than its factorization.

665117981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60465282.

The product of its digits is 90720, while the sum is 44.

The square root of 665117981 is about 25789.8813684747. The cubic root of 665117981 is about 872.9034894822.

The spelling of 665117981 in words is "six hundred sixty-five million, one hundred seventeen thousand, nine hundred eighty-one".