81293281 has 2 divisors, whose sum is σ = 81293282. Its totient is φ = 81293280.

The previous prime is 81293257. The next prime is 81293287. The reversal of 81293281 is 18239218.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64963600 + 16329681 = 8060^2 + 4041^2 .

It is a cyclic number.

It is not a de Polignac number, because 81293281 - 2⁹ = 81292769 is a prime.

It is a super-2 number, since 2×81293281² = 13217195071489922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81293287) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40646640 + 40646641.

It is an arithmetic number, because the mean of its divisors is an integer number (40646641).

Almost surely, 2^81293281 is an apocalyptic number.

It is an amenable number.

81293281 is a deficient number, since it is larger than the sum of its proper divisors (1).

81293281 is an equidigital number, since it uses as much as digits as its factorization.

81293281 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6912, while the sum is 34.

The square root of 81293281 is about 9016.2786669446. The cubic root of 81293281 is about 433.1964450593.

The spelling of 81293281 in words is "eighty-one million, two hundred ninety-three thousand, two hundred eighty-one".