999663 has 16 divisors (see below), whose sum is σ = 1537536. Its totient is φ = 565920.

The previous prime is 999653. The next prime is 999667. The reversal of 999663 is 366999.

It is not a de Polignac number, because 999663 - 2⁵ = 999631 is a prime.

It is a super-2 number, since 2×999663² = 1998652227138, which contains 22 as substring.

999663 is a lucky number.

It is a nialpdrome in base 10.

It is a congruent number.

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 15 ways as a sum of consecutive naturals, for example, 3670 + ... + 3932.

It is an arithmetic number, because the mean of its divisors is an integer number (96096).

2⁹⁹⁹⁶⁶³ is an apocalyptic number.

999663 is a deficient number, since it is larger than the sum of its proper divisors (537873).

999663 is a wasteful number, since it uses less digits than its factorization.

999663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 454.

The product of its digits is 78732, while the sum is 42.

The square root of 999663 is about 999.8314858015. The cubic root of 999663 is about 99.9887654046.

The spelling of 999663 in words is "nine hundred ninety-nine thousand, six hundred sixty-three".