665944 has 8 divisors (see below), whose sum is σ = 1248660. Its totient is φ = 332968.

The previous prime is 665923. The next prime is 665947. The reversal of 665944 is 449566.

665944 = T₁₄₂ + T₁₄₃ + ... + T₁₈₉.

It is a tau number, because it is divible by the number of its divisors (8).

It is a super-2 number, since 2×665944² = 886962822272, which contains 22 as substring.

It is a plaindrome in base 9.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665947) by changing a digit.

665944 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 41614 + ... + 41629.

2⁶⁶⁵⁹⁴⁴ is an apocalyptic number.

It is an amenable number.

665944 is a deficient number, since it is larger than the sum of its proper divisors (582716).

665944 is a wasteful number, since it uses less digits than its factorization.

665944 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83249 (or 83245 counting only the distinct ones).

The product of its digits is 25920, while the sum is 34.

The square root of 665944 is about 816.0539197872. The cubic root of 665944 is about 87.3264696870.

It can be divided in two parts, 665 and 944, that multiplied together give a triangular number (627760 = T₁₁₂₀).

The spelling of 665944 in words is "six hundred sixty-five thousand, nine hundred forty-four".