81812140 has 24 divisors (see below), whose sum is σ = 172200672. Its totient is φ = 32649600.

The previous prime is 81812117. The next prime is 81812147. The reversal of 81812140 is 4121818.

It is not an unprimeable number, because it can be changed into a prime (81812147) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4665 + ... + 13615.

It is an arithmetic number, because the mean of its divisors is an integer number (7175028).

Almost surely, 2^81812140 is an apocalyptic number.

It is an amenable number.

81812140 is an abundant number, since it is smaller than the sum of its proper divisors (90388532).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81812140 is a wasteful number, since it uses less digits than its factorization.

81812140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9417 (or 9415 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 25.

The square root of 81812140 is about 9045.0063571011. The cubic root of 81812140 is about 434.1161248575.

Adding to 81812140 its reverse (4121818), we get a palindrome (85933958).

The spelling of 81812140 in words is "eighty-one million, eight hundred twelve thousand, one hundred forty".