665668 has 6 divisors (see below), whose sum is σ = 1164926. Its totient is φ = 332832.

The previous prime is 665659. The next prime is 665677. The reversal of 665668 is 866566.

It is an interprime number because it is at equal distance from previous prime (665659) and next prime (665677).

It can be written as a sum of positive squares in only one way, i.e., 386884 + 278784 = 622^2 + 528^2 .

It is a super-2 number, since 2×665668² = 886227772448, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83205 + ... + 83212.

2⁶⁶⁵⁶⁶⁸ is an apocalyptic number.

It is an amenable number.

665668 is a deficient number, since it is larger than the sum of its proper divisors (499258).

665668 is a wasteful number, since it uses less digits than its factorization.

665668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 166421 (or 166419 counting only the distinct ones).

The product of its digits is 51840, while the sum is 37.

The square root of 665668 is about 815.8847957892. The cubic root of 665668 is about 87.3144038896.

It can be divided in two parts, 6656 and 68, that added together give a square (6724 = 82²).

The spelling of 665668 in words is "six hundred sixty-five thousand, six hundred sixty-eight".