81705539 has 2 divisors, whose sum is σ = 81705540. Its totient is φ = 81705538.

The previous prime is 81705517. The next prime is 81705551. The reversal of 81705539 is 93550718.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81705539 - 2¹⁶ = 81640003 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81705439) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40852769 + 40852770.

It is an arithmetic number, because the mean of its divisors is an integer number (40852770).

Almost surely, 2^81705539 is an apocalyptic number.

81705539 is a deficient number, since it is larger than the sum of its proper divisors (1).

81705539 is an equidigital number, since it uses as much as digits as its factorization.

81705539 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 37800, while the sum is 38.

The square root of 81705539 is about 9039.1116267031. Note that the first 3 decimals coincide. The cubic root of 81705539 is about 433.9274921873.

The spelling of 81705539 in words is "eighty-one million, seven hundred five thousand, five hundred thirty-nine".