1991033641 has 3 divisors (see below), whose sum is σ = 1991078263. Its totient is φ = 1990989020.

The previous prime is 1991033633. The next prime is 1991033689. The reversal of 1991033641 is 1463301991.

The square root of 1991033641 is 44621.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 1973225241 + 17808400 = 44421^2 + 4220^2 .

It is not a de Polignac number, because 1991033641 - 2³ = 1991033633 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1991033641.

It is not an unprimeable number, because it can be changed into a prime (1991034641) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 22311 + ... + 66931.

Almost surely, 2^1991033641 is an apocalyptic number.

1991033641 is the 44621-st square number.

1991033641 is the 22311-st centered octagonal number.

It is an amenable number.

1991033641 is a deficient number, since it is larger than the sum of its proper divisors (44622).

1991033641 is an frugal number, since it uses more digits than its factorization.

1991033641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89242 (or 44621 counting only the distinct ones).

The product of its (nonzero) digits is 17496, while the sum is 37.

The cubic root of 1991033641 is about 1258.0354117890.

The spelling of 1991033641 in words is "one billion, nine hundred ninety-one million, thirty-three thousand, six hundred forty-one".