81705571 has 2 divisors, whose sum is σ = 81705572. Its totient is φ = 81705570.

The previous prime is 81705563. The next prime is 81705623. The reversal of 81705571 is 17550718.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81705571 - 2³ = 81705563 is a prime.

It is not a weakly prime, because it can be changed into another prime (81705511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40852785 + 40852786.

It is an arithmetic number, because the mean of its divisors is an integer number (40852786).

Almost surely, 2^81705571 is an apocalyptic number.

81705571 is a deficient number, since it is larger than the sum of its proper divisors (1).

81705571 is an equidigital number, since it uses as much as digits as its factorization.

81705571 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9800, while the sum is 34.

The square root of 81705571 is about 9039.1133967884. The cubic root of 81705571 is about 433.9275488365.

The spelling of 81705571 in words is "eighty-one million, seven hundred five thousand, five hundred seventy-one".