181981939 has 2 divisors, whose sum is σ = 181981940. Its totient is φ = 181981938.

The previous prime is 181981937. The next prime is 181981963. The reversal of 181981939 is 939189181.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 181981939 - 2¹ = 181981937 is a prime.

It is a super-2 number, since 2×181981939² = 66234852244399442, which contains 22 as substring.

Together with 181981937, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 181981892 and 181981901.

It is not a weakly prime, because it can be changed into another prime (181981937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90990969 + 90990970.

It is an arithmetic number, because the mean of its divisors is an integer number (90990970).

Almost surely, 2^181981939 is an apocalyptic number.

181981939 is a deficient number, since it is larger than the sum of its proper divisors (1).

181981939 is an equidigital number, since it uses as much as digits as its factorization.

181981939 is an evil number, because the sum of its binary digits is even.

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

The square root of 181981939 is about 13490.0681614290. The cubic root of 181981939 is about 566.6863642903.

The spelling of 181981939 in words is "one hundred eighty-one million, nine hundred eighty-one thousand, nine hundred thirty-nine".