1991781792 has 768 divisors, whose sum is σ = 8128512000. Its totient is φ = 467389440.

The previous prime is 1991781791. The next prime is 1991781833. The reversal of 1991781792 is 2971871991.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (1991781791) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 42378313 + ... + 42378359.

It is an arithmetic number, because the mean of its divisors is an integer number (10584000).

Almost surely, 2^1991781792 is an apocalyptic number.

1991781792 is a gapful number since it is divisible by the number (12) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1991781792, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (4064256000).

1991781792 is an abundant number, since it is smaller than the sum of its proper divisors (6136730208).

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

1991781792 is a wasteful number, since it uses less digits than its factorization.

1991781792 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 111 (or 83 counting only the distinct ones).

The product of its digits is 571536, while the sum is 54.

The square root of 1991781792 is about 44629.3826083221. The cubic root of 1991781792 is about 1258.1929652273.

The spelling of 1991781792 in words is "one billion, nine hundred ninety-one million, seven hundred eighty-one thousand, seven hundred ninety-two".