81291193 has 2 divisors, whose sum is σ = 81291194. Its totient is φ = 81291192.

The previous prime is 81291191. The next prime is 81291209. The reversal of 81291193 is 39119218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78004224 + 3286969 = 8832^2 + 1813^2 .

It is a cyclic number.

It is not a de Polignac number, because 81291193 - 2¹ = 81291191 is a prime.

Together with 81291191, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81291191) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40645596 + 40645597.

It is an arithmetic number, because the mean of its divisors is an integer number (40645597).

Almost surely, 2^81291193 is an apocalyptic number.

It is an amenable number.

81291193 is a deficient number, since it is larger than the sum of its proper divisors (1).

81291193 is an equidigital number, since it uses as much as digits as its factorization.

81291193 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3888, while the sum is 34.

The square root of 81291193 is about 9016.1628756362. The cubic root of 81291193 is about 433.1927361758.

The spelling of 81291193 in words is "eighty-one million, two hundred ninety-one thousand, one hundred ninety-three".