1991221144 has 32 divisors (see below), whose sum is σ = 4094090640. Its totient is φ = 900403200.

The previous prime is 1991221123. The next prime is 1991221163. The reversal of 1991221144 is 4411221991.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 41637 + ... + 75604.

Almost surely, 2^1991221144 is an apocalyptic number.

It is an amenable number.

1991221144 is an abundant number, since it is smaller than the sum of its proper divisors (2102869496).

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

1991221144 is a wasteful number, since it uses less digits than its factorization.

1991221144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117451 (or 117447 counting only the distinct ones).

The product of its digits is 5184, while the sum is 34.

The square root of 1991221144 is about 44623.1010128162. The cubic root of 1991221144 is about 1258.0749018315.

The spelling of 1991221144 in words is "one billion, nine hundred ninety-one million, two hundred twenty-one thousand, one hundred forty-four".