81533791 has 2 divisors, whose sum is σ = 81533792. Its totient is φ = 81533790.

The previous prime is 81533747. The next prime is 81533797. The reversal of 81533791 is 19733518.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81533791 - 2⁹ = 81533279 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81533791.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81533797) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40766895 + 40766896.

It is an arithmetic number, because the mean of its divisors is an integer number (40766896).

Almost surely, 2^81533791 is an apocalyptic number.

81533791 is a deficient number, since it is larger than the sum of its proper divisors (1).

81533791 is an equidigital number, since it uses as much as digits as its factorization.

81533791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 22680, while the sum is 37.

The square root of 81533791 is about 9029.6063590834. The cubic root of 81533791 is about 433.6232351368.

The spelling of 81533791 in words is "eighty-one million, five hundred thirty-three thousand, seven hundred ninety-one".