1991238534 has 12 divisors (see below), whose sum is σ = 4314350196. Its totient is φ = 663746172.

The previous prime is 1991238527. The next prime is 1991238581. The reversal of 1991238534 is 4358321991.

It is a happy number.

1991238534 is a `hidden beast` number, since 1 + 9 + 91 + 23 + 8 + 534 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 1991238534.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 55312164 + ... + 55312199.

It is an arithmetic number, because the mean of its divisors is an integer number (359529183).

Almost surely, 2^1991238534 is an apocalyptic number.

1991238534 is an abundant number, since it is smaller than the sum of its proper divisors (2323111662).

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

1991238534 is a wasteful number, since it uses less digits than its factorization.

1991238534 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110624371 (or 110624368 counting only the distinct ones).

The product of its digits is 233280, while the sum is 45.

The square root of 1991238534 is about 44623.2958666211. The cubic root of 1991238534 is about 1258.0785642171.

The spelling of 1991238534 in words is "one billion, nine hundred ninety-one million, two hundred thirty-eight thousand, five hundred thirty-four".