81128609 has 2 divisors, whose sum is σ = 81128610. Its totient is φ = 81128608.

The previous prime is 81128603. The next prime is 81128629. The reversal of 81128609 is 90682118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76177984 + 4950625 = 8728^2 + 2225^2 .

It is a cyclic number.

It is not a de Polignac number, because 81128609 - 2²⁴ = 64351393 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81128603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40564304 + 40564305.

It is an arithmetic number, because the mean of its divisors is an integer number (40564305).

Almost surely, 2^81128609 is an apocalyptic number.

It is an amenable number.

81128609 is a deficient number, since it is larger than the sum of its proper divisors (1).

81128609 is an equidigital number, since it uses as much as digits as its factorization.

81128609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6912, while the sum is 35.

The square root of 81128609 is about 9007.1421105698. The cubic root of 81128609 is about 432.9037454032.

The spelling of 81128609 in words is "eighty-one million, one hundred twenty-eight thousand, six hundred nine".