81428569 has 2 divisors, whose sum is σ = 81428570. Its totient is φ = 81428568.

The previous prime is 81428531. The next prime is 81428587. The reversal of 81428569 is 96582418.

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., 80192025 + 1236544 = 8955^2 + 1112^2 .

It is a cyclic number.

It is not a de Polignac number, because 81428569 - 2⁹ = 81428057 is a prime.

It is a super-2 number, since 2×81428569² = 13261223698775522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81428519) 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, 40714284 + 40714285.

It is an arithmetic number, because the mean of its divisors is an integer number (40714285).

Almost surely, 2^81428569 is an apocalyptic number.

It is an amenable number.

81428569 is a deficient number, since it is larger than the sum of its proper divisors (1).

81428569 is an equidigital number, since it uses as much as digits as its factorization.

81428569 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 81428569 is about 9023.7779782085. Note that the first 3 decimals coincide. The cubic root of 81428569 is about 433.4366198895.

The spelling of 81428569 in words is "eighty-one million, four hundred twenty-eight thousand, five hundred sixty-nine".