81831643 has 4 divisors (see below), whose sum is σ = 83218680. Its totient is φ = 80444608.

The previous prime is 81831637. The next prime is 81831647. The reversal of 81831643 is 34613818.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 34613818 = 2 ⋅17306909.

It is a cyclic number.

It is not a de Polignac number, because 81831643 - 2⁵ = 81831611 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81831599 and 81831608.

It is not an unprimeable number, because it can be changed into a prime (81831647) 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, 693430 + ... + 693547.

It is an arithmetic number, because the mean of its divisors is an integer number (20804670).

Almost surely, 2^81831643 is an apocalyptic number.

81831643 is a deficient number, since it is larger than the sum of its proper divisors (1387037).

81831643 is a wasteful number, since it uses less digits than its factorization.

81831643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1387036.

The product of its digits is 13824, while the sum is 34.

The square root of 81831643 is about 9046.0844015519. The cubic root of 81831643 is about 434.1506180843.

The spelling of 81831643 in words is "eighty-one million, eight hundred thirty-one thousand, six hundred forty-three".