665931561 has 8 divisors (see below), whose sum is σ = 888118560. Its totient is φ = 443849472.

The previous prime is 665931547. The next prime is 665931569. The reversal of 665931561 is 165139566.

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

It is not a de Polignac number, because 665931561 - 2¹⁰ = 665930537 is a prime.

It is not an unprimeable number, because it can be changed into a prime (665931569) 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, 9976 + ... + 37833.

It is an arithmetic number, because the mean of its divisors is an integer number (111014820).

Almost surely, 2^665931561 is an apocalyptic number.

It is an amenable number.

665931561 is a deficient number, since it is larger than the sum of its proper divisors (222186999).

665931561 is a wasteful number, since it uses less digits than its factorization.

665931561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52455.

The product of its digits is 145800, while the sum is 42.

The square root of 665931561 is about 25805.6497883700. The cubic root of 665931561 is about 873.2592596726.

The spelling of 665931561 in words is "six hundred sixty-five million, nine hundred thirty-one thousand, five hundred sixty-one".