81028391 has 2 divisors, whose sum is σ = 81028392. Its totient is φ = 81028390.

The previous prime is 81028373. The next prime is 81028397. The reversal of 81028391 is 19382018.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81028391 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81028397) 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, 40514195 + 40514196.

It is an arithmetic number, because the mean of its divisors is an integer number (40514196).

Almost surely, 2^81028391 is an apocalyptic number.

81028391 is a deficient number, since it is larger than the sum of its proper divisors (1).

81028391 is an equidigital number, since it uses as much as digits as its factorization.

81028391 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 81028391 is about 9001.5771395906. The cubic root of 81028391 is about 432.7254169249.

The spelling of 81028391 in words is "eighty-one million, twenty-eight thousand, three hundred ninety-one".