1991099020 has 12 divisors (see below), whose sum is σ = 4181307984. Its totient is φ = 796439600.

The previous prime is 1991098981. The next prime is 1991099027. The reversal of 1991099020 is 209901991.

It is not an unprimeable number, because it can be changed into a prime (1991099027) 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, 49777456 + ... + 49777495.

It is an arithmetic number, because the mean of its divisors is an integer number (348442332).

Almost surely, 2^1991099020 is an apocalyptic number.

1991099020 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1991099020 is an abundant number, since it is smaller than the sum of its proper divisors (2190208964).

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

1991099020 is a wasteful number, since it uses less digits than its factorization.

1991099020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99554960 (or 99554958 counting only the distinct ones).

The product of its (nonzero) digits is 13122, while the sum is 40.

The square root of 1991099020 is about 44621.7325974687. The cubic root of 1991099020 is about 1258.0491815542.

The spelling of 1991099020 in words is "one billion, nine hundred ninety-one million, ninety-nine thousand, twenty".