81319289 has 2 divisors, whose sum is σ = 81319290. Its totient is φ = 81319288.

The previous prime is 81319267. The next prime is 81319291. The reversal of 81319289 is 98291318.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 77299264 + 4020025 = 8792^2 + 2005^2 .

It is a cyclic number.

It is not a de Polignac number, because 81319289 - 2²⁴ = 64542073 is a prime.

It is a super-2 number, since 2×81319289² = 13225653526931042, which contains 22 as substring.

Together with 81319291, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81310289) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40659644 + 40659645.

It is an arithmetic number, because the mean of its divisors is an integer number (40659645).

Almost surely, 2^81319289 is an apocalyptic number.

It is an amenable number.

81319289 is a deficient number, since it is larger than the sum of its proper divisors (1).

81319289 is an equidigital number, since it uses as much as digits as its factorization.

81319289 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31104, while the sum is 41.

The square root of 81319289 is about 9017.7208317845. The cubic root of 81319289 is about 433.2426373633.

It can be divided in two parts, 813 and 19289, that added together give a palindrome (20102).

The spelling of 81319289 in words is "eighty-one million, three hundred nineteen thousand, two hundred eighty-nine".