90999 has 6 divisors (see below), whose sum is σ = 131456. Its totient is φ = 60660.

The previous prime is 90997. The next prime is 91009. The reversal of 90999 is 99909.

It is not a de Polignac number, because 90999 - 2¹ = 90997 is a prime.

It is a Duffinian number.

90999 is a modest number, since divided by 999 gives 90 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (90997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 5047 + ... + 5064.

2⁹⁰⁹⁹⁹ is an apocalyptic number.

90999 is a deficient number, since it is larger than the sum of its proper divisors (40457).

90999 is a wasteful number, since it uses less digits than its factorization.

90999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10117 (or 10114 counting only the distinct ones).

The product of its (nonzero) digits is 6561, while the sum is 36.

The square root of 90999 is about 301.6604050916. The cubic root of 90999 is about 44.9792496924.

It can be divided in two parts, 90 and 999, that added together give a square (1089 = 33²).

The spelling of 90999 in words is "ninety thousand, nine hundred ninety-nine".