665625961 has 48 divisors (see below), whose sum is σ = 916163584. Its totient is φ = 470448000.

The previous prime is 665625949. The next prime is 665625991. The reversal of 665625961 is 169526566.

It is a happy number.

It is not a de Polignac number, because 665625961 - 2⁷ = 665625833 is a prime.

It is not an unprimeable number, because it can be changed into a prime (665625941) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 671176 + ... + 672166.

Almost surely, 2^665625961 is an apocalyptic number.

665625961 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

665625961 is a deficient number, since it is larger than the sum of its proper divisors (250537623).

665625961 is a wasteful number, since it uses less digits than its factorization.

665625961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1094 (or 1083 counting only the distinct ones).

The product of its digits is 583200, while the sum is 46.

The square root of 665625961 is about 25799.7279249220. The cubic root of 665625961 is about 873.1256579242.

It can be divided in two parts, 665 and 625961, that added together give a palindrome (626626).

The spelling of 665625961 in words is "six hundred sixty-five million, six hundred twenty-five thousand, nine hundred sixty-one".