665984 has 48 divisors (see below), whose sum is σ = 1492260. Its totient is φ = 295680.

The previous prime is 665983. The next prime is 665993. The reversal of 665984 is 489566.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665981) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 15467 + ... + 15509.

2⁶⁶⁵⁹⁸⁴ is an apocalyptic number.

665984 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 665984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (746130).

665984 is an abundant number, since it is smaller than the sum of its proper divisors (826276).

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

665984 is a wasteful number, since it uses less digits than its factorization.

665984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79 (or 56 counting only the distinct ones).

The product of its digits is 51840, while the sum is 38.

The square root of 665984 is about 816.0784276036. The cubic root of 665984 is about 87.3282180767.

The spelling of 665984 in words is "six hundred sixty-five thousand, nine hundred eighty-four".