81705563 has 2 divisors, whose sum is σ = 81705564.
Its totient is φ = 81705562.
The previous prime is 81705551. The next prime is 81705571. The reversal of 81705563 is 36550718.
It is a strong prime.
It is a cyclic number.
It is not a de Polignac number, because 81705563 - 212 = 81701467 is a prime.
It is not a weakly prime, because it can be changed into another prime (81704563) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (17) of ones.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40852781 + 40852782.
It is an arithmetic number, because the mean of its divisors is an integer number (40852782).
Almost surely, 281705563 is an apocalyptic number.
81705563 is a deficient number, since it is larger than the sum of its proper divisors (1).
81705563 is an equidigital number, since it uses as much as digits as its factorization.
81705563 is an odious number, because the sum of its binary digits is odd.
The product of its (nonzero) digits is 25200, while the sum is 35.
The square root of 81705563 is about 9039.1129542671.
The cubic root of 81705563 is about 433.9275346742.
The spelling of 81705563 in words is "eighty-one million, seven hundred five thousand, five hundred sixty-three".