81731828 has 6 divisors (see below), whose sum is σ = 143030706. Its totient is φ = 40865912.

The previous prime is 81731827. The next prime is 81731849. The reversal of 81731828 is 82813718.

It can be written as a sum of positive squares in only one way, i.e., 77228944 + 4502884 = 8788^2 + 2122^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81731791 and 81731800.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81731821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10216475 + ... + 10216482.

It is an arithmetic number, because the mean of its divisors is an integer number (23838451).

Almost surely, 2^81731828 is an apocalyptic number.

It is an amenable number.

81731828 is a deficient number, since it is larger than the sum of its proper divisors (61298878).

81731828 is a wasteful number, since it uses less digits than its factorization.

81731828 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20432961 (or 20432959 counting only the distinct ones).

The product of its digits is 21504, while the sum is 38.

The square root of 81731828 is about 9040.5656902652. The cubic root of 81731828 is about 433.9740263502.

It can be divided in two parts, 8173 and 1828, that added together give a palindrome (10001).

The spelling of 81731828 in words is "eighty-one million, seven hundred thirty-one thousand, eight hundred twenty-eight".