81185191 has 2 divisors, whose sum is σ = 81185192. Its totient is φ = 81185190.

The previous prime is 81185179. The next prime is 81185201. The reversal of 81185191 is 19158118.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81185191 - 2²¹ = 79088039 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81185891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40592595 + 40592596.

It is an arithmetic number, because the mean of its divisors is an integer number (40592596).

Almost surely, 2^81185191 is an apocalyptic number.

81185191 is a deficient number, since it is larger than the sum of its proper divisors (1).

81185191 is an equidigital number, since it uses as much as digits as its factorization.

81185191 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2880, while the sum is 34.

The square root of 81185191 is about 9010.2825149936. The cubic root of 81185191 is about 433.0043628787.

The spelling of 81185191 in words is "eighty-one million, one hundred eighty-five thousand, one hundred ninety-one".