81866857 has 2 divisors, whose sum is σ = 81866858. Its totient is φ = 81866856.

The previous prime is 81866789. The next prime is 81866879. The reversal of 81866857 is 75866818.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81432576 + 434281 = 9024^2 + 659^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81866857 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81866857.

It is not a weakly prime, because it can be changed into another prime (81866557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40933428 + 40933429.

It is an arithmetic number, because the mean of its divisors is an integer number (40933429).

Almost surely, 2^81866857 is an apocalyptic number.

It is an amenable number.

81866857 is a deficient number, since it is larger than the sum of its proper divisors (1).

81866857 is an equidigital number, since it uses as much as digits as its factorization.

81866857 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 645120, while the sum is 49.

The square root of 81866857 is about 9048.0305591880. The cubic root of 81866857 is about 434.2128840851.

The spelling of 81866857 in words is "eighty-one million, eight hundred sixty-six thousand, eight hundred fifty-seven".