81139199 has 2 divisors, whose sum is σ = 81139200. Its totient is φ = 81139198.

The previous prime is 81139171. The next prime is 81139217. The reversal of 81139199 is 99193118.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81139199 is a prime.

It is a super-2 number, since 2×81139199² = 13167139228723202, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81139109) 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, 40569599 + 40569600.

It is an arithmetic number, because the mean of its divisors is an integer number (40569600).

Almost surely, 2^81139199 is an apocalyptic number.

81139199 is a deficient number, since it is larger than the sum of its proper divisors (1).

81139199 is an equidigital number, since it uses as much as digits as its factorization.

81139199 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17496, while the sum is 41.

The square root of 81139199 is about 9007.7299582081. The cubic root of 81139199 is about 432.9225807285.

The spelling of 81139199 in words is "eighty-one million, one hundred thirty-nine thousand, one hundred ninety-nine".