1991349431 has 4 divisors (see below), whose sum is σ = 2011065864. Its totient is φ = 1971633000.

The previous prime is 1991349379. The next prime is 1991349433. The reversal of 1991349431 is 1349431991.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1991349431 is a prime.

It is a super-2 number, since 2×1991349431² = 7930945112688047522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991349433) 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, 9858065 + ... + 9858266.

It is an arithmetic number, because the mean of its divisors is an integer number (502766466).

Almost surely, 2^1991349431 is an apocalyptic number.

1991349431 is a deficient number, since it is larger than the sum of its proper divisors (19716433).

1991349431 is a wasteful number, since it uses less digits than its factorization.

1991349431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19716432.

The product of its digits is 104976, while the sum is 44.

The square root of 1991349431 is about 44624.5384401901. The cubic root of 1991349431 is about 1258.1019189527.

The spelling of 1991349431 in words is "one billion, nine hundred ninety-one million, three hundred forty-nine thousand, four hundred thirty-one".