1997991121 has 32 divisors (see below), whose sum is σ = 2381414400. Its totient is φ = 1675186128.

The previous prime is 1997991119. The next prime is 1997991167. The reversal of 1997991121 is 1211997991.

It is not a de Polignac number, because 1997991121 - 2¹ = 1997991119 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (49).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1997991101) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5216496 + ... + 5216878.

It is an arithmetic number, because the mean of its divisors is an integer number (74419200).

Almost surely, 2^1997991121 is an apocalyptic number.

It is an amenable number.

1997991121 is a deficient number, since it is larger than the sum of its proper divisors (383423279).

1997991121 is an equidigital number, since it uses as much as digits as its factorization.

1997991121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 698 (or 684 counting only the distinct ones).

The product of its digits is 91854, while the sum is 49.

The square root of 1997991121 is about 44698.8939572334. The cubic root of 1997991121 is about 1259.4990704226.

The spelling of 1997991121 in words is "one billion, nine hundred ninety-seven million, nine hundred ninety-one thousand, one hundred twenty-one".