81255221 has 2 divisors, whose sum is σ = 81255222. Its totient is φ = 81255220.

The previous prime is 81255203. The next prime is 81255241. The reversal of 81255221 is 12255218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81252196 + 3025 = 9014^2 + 55^2 .

It is a cyclic number.

It is not a de Polignac number, because 81255221 - 2⁶ = 81255157 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81255241) 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, 40627610 + 40627611.

It is an arithmetic number, because the mean of its divisors is an integer number (40627611).

Almost surely, 2^81255221 is an apocalyptic number.

It is an amenable number.

81255221 is a deficient number, since it is larger than the sum of its proper divisors (1).

81255221 is an equidigital number, since it uses as much as digits as its factorization.

81255221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1600, while the sum is 26.

The square root of 81255221 is about 9014.1677929801. The cubic root of 81255221 is about 433.1288296705.

The spelling of 81255221 in words is "eighty-one million, two hundred fifty-five thousand, two hundred twenty-one".