665631 has 16 divisors (see below), whose sum is σ = 1000800. Its totient is φ = 437184.

The previous prime is 665629. The next prime is 665633. The reversal of 665631 is 136566.

665631 is a `hidden beast` number, since 6 + 656 + 3 + 1 = 666.

It is an interprime number because it is at equal distance from previous prime (665629) and next prime (665633).

It is not a de Polignac number, because 665631 - 2¹ = 665629 is a prime.

It is a super-2 number, since 2×665631² = 886129256322, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 665595 and 665604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665633) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2265 + ... + 2541.

It is an arithmetic number, because the mean of its divisors is an integer number (62550).

2⁶⁶⁵⁶³¹ is an apocalyptic number.

665631 is a deficient number, since it is larger than the sum of its proper divisors (335169).

665631 is a wasteful number, since it uses less digits than its factorization.

665631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 375 (or 369 counting only the distinct ones).

The product of its digits is 3240, while the sum is 27.

The square root of 665631 is about 815.8621207042. The cubic root of 665631 is about 87.3127861198.

It can be divided in two parts, 66563 and 1, that added together give a square (66564 = 258²).

The spelling of 665631 in words is "six hundred sixty-five thousand, six hundred thirty-one".