665431601 has 4 divisors (see below), whose sum is σ = 665492772. Its totient is φ = 665370432.

The previous prime is 665431553. The next prime is 665431631. The reversal of 665431601 is 106134566.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 489471376 + 175960225 = 22124^2 + 13265^2 .

It is a cyclic number.

It is not a de Polignac number, because 665431601 - 2⁶ = 665431537 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (665431631) 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, 9356 + ... + 37661.

It is an arithmetic number, because the mean of its divisors is an integer number (166373193).

Almost surely, 2^665431601 is an apocalyptic number.

It is an amenable number.

665431601 is a deficient number, since it is larger than the sum of its proper divisors (61171).

665431601 is a wasteful number, since it uses less digits than its factorization.

665431601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61170.

The product of its (nonzero) digits is 12960, while the sum is 32.

The square root of 665431601 is about 25795.9609435276. The cubic root of 665431601 is about 873.0406666364.

The spelling of 665431601 in words is "six hundred sixty-five million, four hundred thirty-one thousand, six hundred one".