81555317 has 2 divisors, whose sum is σ = 81555318. Its totient is φ = 81555316.

The previous prime is 81555311. The next prime is 81555329. The reversal of 81555317 is 71355518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 56415121 + 25140196 = 7511^2 + 5014^2 .

It is a cyclic number.

It is not a de Polignac number, because 81555317 - 2¹² = 81551221 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81555311) 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, 40777658 + 40777659.

It is an arithmetic number, because the mean of its divisors is an integer number (40777659).

Almost surely, 2^81555317 is an apocalyptic number.

It is an amenable number.

81555317 is a deficient number, since it is larger than the sum of its proper divisors (1).

81555317 is an equidigital number, since it uses as much as digits as its factorization.

81555317 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 21000, while the sum is 35.

The square root of 81555317 is about 9030.7982482170. The cubic root of 81555317 is about 433.6613925368.

The spelling of 81555317 in words is "eighty-one million, five hundred fifty-five thousand, three hundred seventeen".