991904 has 24 divisors (see below), whose sum is σ = 1975680. Its totient is φ = 490176.

The previous prime is 991901. The next prime is 991909. The reversal of 991904 is 409199.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is not an unprimeable number, because it can be changed into a prime (991901) 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, 4337 + ... + 4559.

It is an arithmetic number, because the mean of its divisors is an integer number (82320).

2⁹⁹¹⁹⁰⁴ is an apocalyptic number.

It is an amenable number.

991904 is a deficient number, since it is larger than the sum of its proper divisors (983776).

991904 is a wasteful number, since it uses less digits than its factorization.

991904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 372 (or 364 counting only the distinct ones).

The product of its (nonzero) digits is 2916, while the sum is 32.

The square root of 991904 is about 995.9437735133. The cubic root of 991904 is about 99.7294017597.

Adding to 991904 its sum of digits (32), we get a triangular number (991936 = T₁₄₀₈).

The spelling of 991904 in words is "nine hundred ninety-one thousand, nine hundred four".