81397769 has 2 divisors, whose sum is σ = 81397770. Its totient is φ = 81397768.

The previous prime is 81397739. The next prime is 81397777. The reversal of 81397769 is 96779318.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 79423744 + 1974025 = 8912^2 + 1405^2 .

It is a cyclic number.

It is not a de Polignac number, because 81397769 - 2²⁰ = 80349193 is a prime.

It is a super-2 number, since 2×81397769² = 13251193596354722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81397739) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40698884 + 40698885.

It is an arithmetic number, because the mean of its divisors is an integer number (40698885).

Almost surely, 2^81397769 is an apocalyptic number.

It is an amenable number.

81397769 is a deficient number, since it is larger than the sum of its proper divisors (1).

81397769 is an equidigital number, since it uses as much as digits as its factorization.

81397769 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 571536, while the sum is 50.

The square root of 81397769 is about 9022.0712145272. The cubic root of 81397769 is about 433.3819644961.

The spelling of 81397769 in words is "eighty-one million, three hundred ninety-seven thousand, seven hundred sixty-nine".