1991001992 has 32 divisors (see below), whose sum is σ = 4451932800. Its totient is φ = 816186624.

The previous prime is 1991001983. The next prime is 1991002007. The reversal of 1991001992 is 2991001991.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 771617 + ... + 774192.

It is an arithmetic number, because the mean of its divisors is an integer number (139122900).

Almost surely, 2^1991001992 is an apocalyptic number.

It is an amenable number.

1991001992 is an abundant number, since it is smaller than the sum of its proper divisors (2460930808).

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

1991001992 is a wasteful number, since it uses less digits than its factorization.

1991001992 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1545845 (or 1545841 counting only the distinct ones).

The product of its (nonzero) digits is 13122, while the sum is 41.

The square root of 1991001992 is about 44620.6453561577. The cubic root of 1991001992 is about 1258.0287459425.

Subtracting 1991001992 from its reverse (2991001991), we obtain a palindrome (999999999).

The spelling of 1991001992 in words is "one billion, nine hundred ninety-one million, one thousand, nine hundred ninety-two".