81569 has 2 divisors, whose sum is σ = 81570. Its totient is φ = 81568.

The previous prime is 81563. The next prime is 81611. The reversal of 81569 is 96518.

81569 is an esthetic number in base 7, because in such base its adjacent digits differ by 1.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 46225 + 35344 = 215^2 + 188^2 .

It is a cyclic number.

It is not a de Polignac number, because 81569 - 2⁴ = 81553 is a prime.

It is a super-2 number, since 2×81569² = 13307003522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40784 + 40785.

It is an arithmetic number, because the mean of its divisors is an integer number (40785).

2⁸¹⁵⁶⁹ is an apocalyptic number.

It is an amenable number.

81569 is a deficient number, since it is larger than the sum of its proper divisors (1).

81569 is an equidigital number, since it uses as much as digits as its factorization.

81569 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2160, while the sum is 29.

The square root of 81569 is about 285.6028711340. The cubic root of 81569 is about 43.3685643794.

The spelling of 81569 in words is "eighty-one thousand, five hundred sixty-nine".