1991881692 has 42 divisors (see below), whose sum is σ = 5226306288. Its totient is φ = 663959592.

The previous prime is 1991881681. The next prime is 1991881709. The reversal of 1991881692 is 2961881991.

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 338628 + ... + 344459.

It is an arithmetic number, because the mean of its divisors is an integer number (124435864).

Almost surely, 2^1991881692 is an apocalyptic number.

1991881692 is a gapful number since it is divisible by the number (12) formed by its first and last digit.

It is an amenable number.

1991881692 is an abundant number, since it is smaller than the sum of its proper divisors (3234424596).

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

1991881692 is an equidigital number, since it uses as much as digits as its factorization.

1991881692 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 683109 (or 683092 counting only the distinct ones).

The product of its digits is 559872, while the sum is 54.

The square root of 1991881692 is about 44630.5018121016. The cubic root of 1991881692 is about 1258.2140002249.

The spelling of 1991881692 in words is "one billion, nine hundred ninety-one million, eight hundred eighty-one thousand, six hundred ninety-two".