81705623 has 2 divisors, whose sum is σ = 81705624. Its totient is φ = 81705622.

The previous prime is 81705571. The next prime is 81705653. The reversal of 81705623 is 32650718.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81705623 is a prime.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81705623.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81705653) 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, 40852811 + 40852812.

It is an arithmetic number, because the mean of its divisors is an integer number (40852812).

Almost surely, 2^81705623 is an apocalyptic number.

81705623 is a deficient number, since it is larger than the sum of its proper divisors (1).

81705623 is an equidigital number, since it uses as much as digits as its factorization.

81705623 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 81705623 is about 9039.1162731763. The cubic root of 81705623 is about 433.9276408916.

It can be divided in two parts, 81705 and 623, that added together give a palindrome (82328).

The spelling of 81705623 in words is "eighty-one million, seven hundred five thousand, six hundred twenty-three".