81728531 has 2 divisors, whose sum is σ = 81728532. Its totient is φ = 81728530.

The previous prime is 81728513. The next prime is 81728561. The reversal of 81728531 is 13582718.

Together with previous prime (81728513) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81728531 - 2¹⁰ = 81727507 is a prime.

It is a super-2 number, since 2×81728531² = 13359105558835922, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 81728491 and 81728500.

It is not a weakly prime, because it can be changed into another prime (81728501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40864265 + 40864266.

It is an arithmetic number, because the mean of its divisors is an integer number (40864266).

Almost surely, 2^81728531 is an apocalyptic number.

81728531 is a deficient number, since it is larger than the sum of its proper divisors (1).

81728531 is an equidigital number, since it uses as much as digits as its factorization.

81728531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13440, while the sum is 35.

The square root of 81728531 is about 9040.3833436420. The cubic root of 81728531 is about 433.9681908773.

The spelling of 81728531 in words is "eighty-one million, seven hundred twenty-eight thousand, five hundred thirty-one".