81128501 has 4 divisors (see below), whose sum is σ = 81146604. Its totient is φ = 81110400.

The previous prime is 81128483. The next prime is 81128513. The reversal of 81128501 is 10582118.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 8708401 + 72420100 = 2951^2 + 8510^2 .

It is a cyclic number.

It is not a de Polignac number, because 81128501 - 2¹⁰ = 81127477 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81128561) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3191 + ... + 13131.

It is an arithmetic number, because the mean of its divisors is an integer number (20286651).

Almost surely, 2^81128501 is an apocalyptic number.

It is an amenable number.

81128501 is a deficient number, since it is larger than the sum of its proper divisors (18103).

81128501 is an equidigital number, since it uses as much as digits as its factorization.

81128501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18102.

The product of its (nonzero) digits is 640, while the sum is 26.

The square root of 81128501 is about 9007.1361153254. The cubic root of 81128501 is about 432.9035533065.

The spelling of 81128501 in words is "eighty-one million, one hundred twenty-eight thousand, five hundred one".