81842569 has 2 divisors, whose sum is σ = 81842570. Its totient is φ = 81842568.

The previous prime is 81842549. The next prime is 81842587. The reversal of 81842569 is 96524818.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81234169 + 608400 = 9013^2 + 780^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81842569 is a prime.

It is a super-2 number, since 2×81842569² = 13396412201039522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81842549) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40921284 + 40921285.

It is an arithmetic number, because the mean of its divisors is an integer number (40921285).

Almost surely, 2^81842569 is an apocalyptic number.

It is an amenable number.

81842569 is a deficient number, since it is larger than the sum of its proper divisors (1).

81842569 is an equidigital number, since it uses as much as digits as its factorization.

81842569 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 138240, while the sum is 43.

The square root of 81842569 is about 9046.6882890923. The cubic root of 81842569 is about 434.1699395366.

The spelling of 81842569 in words is "eighty-one million, eight hundred forty-two thousand, five hundred sixty-nine".