81586613 has 2 divisors, whose sum is σ = 81586614. Its totient is φ = 81586612.

The previous prime is 81586579. The next prime is 81586639. The reversal of 81586613 is 31668518.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 45670564 + 35916049 = 6758^2 + 5993^2 .

It is a cyclic number.

It is not a de Polignac number, because 81586613 - 2¹⁸ = 81324469 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81586693) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40793306 + 40793307.

It is an arithmetic number, because the mean of its divisors is an integer number (40793307).

Almost surely, 2^81586613 is an apocalyptic number.

It is an amenable number.

81586613 is a deficient number, since it is larger than the sum of its proper divisors (1).

81586613 is an equidigital number, since it uses as much as digits as its factorization.

81586613 is an evil number, because the sum of its binary digits is even.

The product of its digits is 34560, while the sum is 38.

The square root of 81586613 is about 9032.5308192112. The cubic root of 81586613 is about 433.7168564509.

The spelling of 81586613 in words is "eighty-one million, five hundred eighty-six thousand, six hundred thirteen".