81994189 has 2 divisors, whose sum is σ = 81994190. Its totient is φ = 81994188.

The previous prime is 81994181. The next prime is 81994193. The reversal of 81994189 is 98149918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 71690089 + 10304100 = 8467^2 + 3210^2 .

It is a cyclic number.

It is not a de Polignac number, because 81994189 - 2³ = 81994181 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 (81994181) by changing a digit.

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, 40997094 + 40997095.

It is an arithmetic number, because the mean of its divisors is an integer number (40997095).

Almost surely, 2^81994189 is an apocalyptic number.

It is an amenable number.

81994189 is a deficient number, since it is larger than the sum of its proper divisors (1).

81994189 is an equidigital number, since it uses as much as digits as its factorization.

81994189 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 186624, while the sum is 49.

The square root of 81994189 is about 9055.0642736537. The cubic root of 81994189 is about 434.4378858215.

The spelling of 81994189 in words is "eighty-one million, nine hundred ninety-four thousand, one hundred eighty-nine".