665681601 has 32 divisors (see below), whose sum is σ = 975744000. Its totient is φ = 401179968.

The previous prime is 665681567. The next prime is 665681603. The reversal of 665681601 is 106186566.

It is not a de Polignac number, because 665681601 - 2⁹ = 665681089 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 665681601.

It is not an unprimeable number, because it can be changed into a prime (665681603) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1009810 + ... + 1010468.

It is an arithmetic number, because the mean of its divisors is an integer number (30492000).

Almost surely, 2^665681601 is an apocalyptic number.

It is an amenable number.

665681601 is a deficient number, since it is larger than the sum of its proper divisors (310062399).

665681601 is a wasteful number, since it uses less digits than its factorization.

665681601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1173.

The product of its (nonzero) digits is 51840, while the sum is 39.

The square root of 665681601 is about 25800.8062083339. The cubic root of 665681601 is about 873.1499855801.

The spelling of 665681601 in words is "six hundred sixty-five million, six hundred eighty-one thousand, six hundred one".