65999 has 4 divisors (see below), whose sum is σ = 68160. Its totient is φ = 63840.

The previous prime is 65993. The next prime is 66029. The reversal of 65999 is 99956.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 65999 - 2⁴ = 65983 is a prime.

It is a Duffinian number.

65999 is a modest number, since divided by 999 gives 65 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (65993) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1034 + ... + 1095.

It is an arithmetic number, because the mean of its divisors is an integer number (17040).

2⁶⁵⁹⁹⁹ is an apocalyptic number.

65999 is a deficient number, since it is larger than the sum of its proper divisors (2161).

65999 is a wasteful number, since it uses less digits than its factorization.

65999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2160.

The product of its digits is 21870, while the sum is 38.

The square root of 65999 is about 256.9027053186. The cubic root of 65999 is about 40.4121961022.

The spelling of 65999 in words is "sixty-five thousand, nine hundred ninety-nine".