81185539 has 2 divisors, whose sum is σ = 81185540. Its totient is φ = 81185538.

The previous prime is 81185521. The next prime is 81185543. The reversal of 81185539 is 93558118.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81185539 - 2¹³ = 81177347 is a prime.

It is not a weakly prime, because it can be changed into another prime (81185549) 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, 40592769 + 40592770.

It is an arithmetic number, because the mean of its divisors is an integer number (40592770).

Almost surely, 2^81185539 is an apocalyptic number.

81185539 is a deficient number, since it is larger than the sum of its proper divisors (1).

81185539 is an equidigital number, since it uses as much as digits as its factorization.

81185539 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 43200, while the sum is 40.

The square root of 81185539 is about 9010.3018262431. The cubic root of 81185539 is about 433.0049815683.

The spelling of 81185539 in words is "eighty-one million, one hundred eighty-five thousand, five hundred thirty-nine".