1991120904 has 24 divisors (see below), whose sum is σ = 5392619310. Its totient is φ = 663706944.

The previous prime is 1991120863. The next prime is 1991120909. The reversal of 1991120904 is 4090211991.

It can be written as a sum of positive squares in only one way, i.e., 1980428004 + 10692900 = 44502^2 + 3270^2 .

It is a tau number, because it is divible by the number of its divisors (24).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (1991120909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 13827157 + ... + 13827300.

Almost surely, 2^1991120904 is an apocalyptic number.

It is an amenable number.

1991120904 is an abundant number, since it is smaller than the sum of its proper divisors (3401498406).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1991120904 is a wasteful number, since it uses less digits than its factorization.

1991120904 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27654469 (or 27654462 counting only the distinct ones).

The product of its (nonzero) digits is 5832, while the sum is 36.

The square root of 1991120904 is about 44621.9778136290. The cubic root of 1991120904 is about 1258.0537905745.

The spelling of 1991120904 in words is "one billion, nine hundred ninety-one million, one hundred twenty thousand, nine hundred four".