81289791 has 32 divisors (see below), whose sum is σ = 132157440. Its totient is φ = 48974400.

The previous prime is 81289753. The next prime is 81289799. The reversal of 81289791 is 19798218.

It is not a de Polignac number, because 81289791 - 2⁹ = 81289279 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81289799) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 56011 + ... + 57443.

It is an arithmetic number, because the mean of its divisors is an integer number (4129920).

Almost surely, 2^81289791 is an apocalyptic number.

81289791 is a deficient number, since it is larger than the sum of its proper divisors (50867649).

81289791 is a wasteful number, since it uses less digits than its factorization.

81289791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1644 (or 1638 counting only the distinct ones).

The product of its digits is 72576, while the sum is 45.

The square root of 81289791 is about 9016.0851260400. The cubic root of 81289791 is about 433.1902457883.

The spelling of 81289791 in words is "eighty-one million, two hundred eighty-nine thousand, seven hundred ninety-one".