81284257 has 2 divisors, whose sum is σ = 81284258. Its totient is φ = 81284256.

The previous prime is 81284221. The next prime is 81284309. The reversal of 81284257 is 75248218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81018001 + 266256 = 9001^2 + 516^2 .

It is a cyclic number.

It is not a de Polignac number, because 81284257 - 2²³ = 72895649 is a prime.

It is not a weakly prime, because it can be changed into another prime (81284207) 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, 40642128 + 40642129.

It is an arithmetic number, because the mean of its divisors is an integer number (40642129).

Almost surely, 2^81284257 is an apocalyptic number.

It is an amenable number.

81284257 is a deficient number, since it is larger than the sum of its proper divisors (1).

81284257 is an equidigital number, since it uses as much as digits as its factorization.

81284257 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 35840, while the sum is 37.

The square root of 81284257 is about 9015.7782248678. The cubic root of 81284257 is about 433.1804154058.

The spelling of 81284257 in words is "eighty-one million, two hundred eighty-four thousand, two hundred fifty-seven".