81705551 has 2 divisors, whose sum is σ = 81705552. Its totient is φ = 81705550.

The previous prime is 81705539. The next prime is 81705563. The reversal of 81705551 is 15550718.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (81705539) and next prime (81705563).

It is a cyclic number.

It is not a de Polignac number, because 81705551 - 2⁶ = 81705487 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81705511) 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, 40852775 + 40852776.

It is an arithmetic number, because the mean of its divisors is an integer number (40852776).

Almost surely, 2^81705551 is an apocalyptic number.

81705551 is a deficient number, since it is larger than the sum of its proper divisors (1).

81705551 is an equidigital number, since it uses as much as digits as its factorization.

81705551 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7000, while the sum is 32.

The square root of 81705551 is about 9039.1122904852. The cubic root of 81705551 is about 433.9275134307.

The spelling of 81705551 in words is "eighty-one million, seven hundred five thousand, five hundred fifty-one".