665658 has 40 divisors (see below), whose sum is σ = 1707552. Its totient is φ = 189864.

The previous prime is 665633. The next prime is 665659. The reversal of 665658 is 856566.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 665658.

It is not an unprimeable number, because it can be changed into a prime (665659) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 841 + ... + 1427.

2⁶⁶⁵⁶⁵⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 665658, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (853776).

665658 is an abundant number, since it is smaller than the sum of its proper divisors (1041894).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

665658 is a wasteful number, since it uses less digits than its factorization.

665658 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 608 (or 599 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 665658 is about 815.8786674500. The cubic root of 665658 is about 87.3139666605.

The spelling of 665658 in words is "six hundred sixty-five thousand, six hundred fifty-eight".