665860 has 36 divisors (see below), whose sum is σ = 1521828. Its totient is φ = 244608.

The previous prime is 665857. The next prime is 665897. The reversal of 665860 is 68566.

665860 = T₂₉ + T₃₀ + ... + T₁₅₈.

It can be written as a sum of positive squares in 6 ways, for example, as 12996 + 652864 = 114^2 + 808^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3282 + ... + 3478.

It is an arithmetic number, because the mean of its divisors is an integer number (42273).

2⁶⁶⁵⁸⁶⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 665860, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (760914).

665860 is an abundant number, since it is smaller than the sum of its proper divisors (855968).

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

665860 is a wasteful number, since it uses less digits than its factorization.

665860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 232 (or 217 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 665860 is about 816.0024509767. The cubic root of 665860 is about 87.3227978408.

It can be divided in two parts, 66 and 5860, that multiplied together give a triangular number (386760 = T₈₇₉).

The spelling of 665860 in words is "six hundred sixty-five thousand, eight hundred sixty".