81319457 has 2 divisors, whose sum is σ = 81319458. Its totient is φ = 81319456.

The previous prime is 81319453. The next prime is 81319531. The reversal of 81319457 is 75491318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 73942801 + 7376656 = 8599^2 + 2716^2 .

It is a cyclic number.

It is not a de Polignac number, because 81319457 - 2² = 81319453 is a prime.

It is a super-2 number, since 2×81319457² = 13225708173549698, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81319457.

It is not a weakly prime, because it can be changed into another prime (81319453) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40659728 + 40659729.

It is an arithmetic number, because the mean of its divisors is an integer number (40659729).

Almost surely, 2^81319457 is an apocalyptic number.

It is an amenable number.

81319457 is a deficient number, since it is larger than the sum of its proper divisors (1).

81319457 is an equidigital number, since it uses as much as digits as its factorization.

81319457 is an evil number, because the sum of its binary digits is even.

The product of its digits is 30240, while the sum is 38.

The square root of 81319457 is about 9017.7301467720. The cubic root of 81319457 is about 433.2429357128.

The spelling of 81319457 in words is "eighty-one million, three hundred nineteen thousand, four hundred fifty-seven".