181991938 has 4 divisors (see below), whose sum is σ = 272987910. Its totient is φ = 90995968.

The previous prime is 181991911. The next prime is 181991941. The reversal of 181991938 is 839199181.

It is a happy number.

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

It can be written as a sum of positive squares in only one way, i.e., 174953529 + 7038409 = 13227^2 + 2653^2 .

It is a junction number, because it is equal to n+sod(n) for n = 181991891 and 181991900.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45497983 + ... + 45497986.

Almost surely, 2^181991938 is an apocalyptic number.

181991938 is a deficient number, since it is larger than the sum of its proper divisors (90995972).

181991938 is an equidigital number, since it uses as much as digits as its factorization.

181991938 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90995971.

The product of its digits is 139968, while the sum is 49.

The square root of 181991938 is about 13490.4387623235. The cubic root of 181991938 is about 566.6967429634.

The spelling of 181991938 in words is "one hundred eighty-one million, nine hundred ninety-one thousand, nine hundred thirty-eight".