81728887 has 2 divisors, whose sum is σ = 81728888. Its totient is φ = 81728886.

The previous prime is 81728869. The next prime is 81728891. The reversal of 81728887 is 78882718.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81728887 - 2¹⁵ = 81696119 is a prime.

It is a super-2 number, since 2×81728887² = 13359221940517538, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81728887.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81728807) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40864443 + 40864444.

It is an arithmetic number, because the mean of its divisors is an integer number (40864444).

Almost surely, 2^81728887 is an apocalyptic number.

81728887 is a deficient number, since it is larger than the sum of its proper divisors (1).

81728887 is an equidigital number, since it uses as much as digits as its factorization.

81728887 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 401408, while the sum is 49.

The square root of 81728887 is about 9040.4030330511. The cubic root of 81728887 is about 433.9688209814.

The spelling of 81728887 in words is "eighty-one million, seven hundred twenty-eight thousand, eight hundred eighty-seven".