81385091 has 2 divisors, whose sum is σ = 81385092. Its totient is φ = 81385090.

The previous prime is 81385081. The next prime is 81385097. The reversal of 81385091 is 19058318.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81385091 is a prime.

It is not a weakly prime, because it can be changed into another prime (81385097) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40692545 + 40692546.

It is an arithmetic number, because the mean of its divisors is an integer number (40692546).

Almost surely, 2^81385091 is an apocalyptic number.

81385091 is a deficient number, since it is larger than the sum of its proper divisors (1).

81385091 is an equidigital number, since it uses as much as digits as its factorization.

81385091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8640, while the sum is 35.

The square root of 81385091 is about 9021.3685768846. The cubic root of 81385091 is about 433.3594630529.

The spelling of 81385091 in words is "eighty-one million, three hundred eighty-five thousand, ninety-one".