665998 has 16 divisors (see below), whose sum is σ = 1044576. Its totient is φ = 318240.

The previous prime is 665993. The next prime is 666013. The reversal of 665998 is 899566.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665993) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6415 + ... + 6517.

It is an arithmetic number, because the mean of its divisors is an integer number (65286).

2⁶⁶⁵⁹⁹⁸ is an apocalyptic number.

665998 is a deficient number, since it is larger than the sum of its proper divisors (378578).

665998 is a wasteful number, since it uses less digits than its factorization.

665998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 219.

The product of its digits is 116640, while the sum is 43.

The square root of 665998 is about 816.0870051655. The cubic root of 665998 is about 87.3288299965.

The spelling of 665998 in words is "six hundred sixty-five thousand, nine hundred ninety-eight".