81399187 has 2 divisors, whose sum is σ = 81399188. Its totient is φ = 81399186.

The previous prime is 81399127. The next prime is 81399191. The reversal of 81399187 is 78199318.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81399187 is a prime.

It is not a weakly prime, because it can be changed into another prime (81399107) 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, 40699593 + 40699594.

It is an arithmetic number, because the mean of its divisors is an integer number (40699594).

Almost surely, 2^81399187 is an apocalyptic number.

81399187 is a deficient number, since it is larger than the sum of its proper divisors (1).

81399187 is an equidigital number, since it uses as much as digits as its factorization.

81399187 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 108864, while the sum is 46.

The square root of 81399187 is about 9022.1497992441. The cubic root of 81399187 is about 433.3844810764.

It can be divided in two parts, 813 and 99187, that added together give a 5-th power (100000 = 10⁵).

The spelling of 81399187 in words is "eighty-one million, three hundred ninety-nine thousand, one hundred eighty-seven".