999665 has 4 divisors (see below), whose sum is σ = 1199604. Its totient is φ = 799728.

The previous prime is 999653. The next prime is 999667. The reversal of 999665 is 566999.

999665 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It can be written as a sum of positive squares in 2 ways, for example, as 169744 + 829921 = 412^2 + 911^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-999665 is a prime.

It is a super-2 number, since 2×999665² = 1998660224450, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a nialpdrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (999667) 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, 99962 + ... + 99971.

It is an arithmetic number, because the mean of its divisors is an integer number (299901).

2⁹⁹⁹⁶⁶⁵ is an apocalyptic number.

It is an amenable number.

999665 is a deficient number, since it is larger than the sum of its proper divisors (199939).

999665 is a wasteful number, since it uses less digits than its factorization.

999665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199938.

The product of its digits is 131220, while the sum is 44.

The square root of 999665 is about 999.8324859695. The cubic root of 999665 is about 99.9888320862.

The spelling of 999665 in words is "nine hundred ninety-nine thousand, six hundred sixty-five".