181661999 has 2 divisors, whose sum is σ = 181662000. Its totient is φ = 181661998.

The previous prime is 181661959. The next prime is 181662007. The reversal of 181661999 is 999166181.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 181661999 - 2⁸ = 181661743 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181661929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90830999 + 90831000.

It is an arithmetic number, because the mean of its divisors is an integer number (90831000).

Almost surely, 2^181661999 is an apocalyptic number.

181661999 is a deficient number, since it is larger than the sum of its proper divisors (1).

181661999 is an equidigital number, since it uses as much as digits as its factorization.

181661999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 209952, while the sum is 50.

The square root of 181661999 is about 13478.2045911167. The cubic root of 181661999 is about 566.3540749239.

The spelling of 181661999 in words is "one hundred eighty-one million, six hundred sixty-one thousand, nine hundred ninety-nine".