1991335439 has 4 divisors (see below), whose sum is σ = 1991991600. Its totient is φ = 1990679280.

The previous prime is 1991335429. The next prime is 1991335447. The reversal of 1991335439 is 9345331991.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9345331991 = 1409 ⋅6632599.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1991335439 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1991335393 and 1991335402.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991335429) 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, 323507 + ... + 329604.

It is an arithmetic number, because the mean of its divisors is an integer number (497997900).

Almost surely, 2^1991335439 is an apocalyptic number.

1991335439 is a deficient number, since it is larger than the sum of its proper divisors (656161).

1991335439 is an equidigital number, since it uses as much as digits as its factorization.

1991335439 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 656160.

The product of its digits is 393660, while the sum is 47.

The square root of 1991335439 is about 44624.3816651839. The cubic root of 1991335439 is about 1258.0989723071.

The spelling of 1991335439 in words is "one billion, nine hundred ninety-one million, three hundred thirty-five thousand, four hundred thirty-nine".