81256213 has 2 divisors, whose sum is σ = 81256214. Its totient is φ = 81256212.

The previous prime is 81256183. The next prime is 81256223. The reversal of 81256213 is 31265218.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 66945124 + 14311089 = 8182^2 + 3783^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81256213 is a prime.

It is a super-2 number, since 2×81256213² = 13205144302202738, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81256223) 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, 40628106 + 40628107.

It is an arithmetic number, because the mean of its divisors is an integer number (40628107).

Almost surely, 2^81256213 is an apocalyptic number.

It is an amenable number.

81256213 is a deficient number, since it is larger than the sum of its proper divisors (1).

81256213 is an equidigital number, since it uses as much as digits as its factorization.

81256213 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2880, while the sum is 28.

The square root of 81256213 is about 9014.2228173038. Note that the first 3 decimals coincide. The cubic root of 81256213 is about 433.1305922733.

The spelling of 81256213 in words is "eighty-one million, two hundred fifty-six thousand, two hundred thirteen".