81540840 has 64 divisors (see below), whose sum is σ = 259018560. Its totient is φ = 20464640.

The previous prime is 81540803. The next prime is 81540853. The reversal of 81540840 is 4804518.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 81540798 and 81540807.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17946 + ... + 22025.

It is an arithmetic number, because the mean of its divisors is an integer number (4047165).

Almost surely, 2^81540840 is an apocalyptic number.

It is an amenable number.

81540840 is an abundant number, since it is smaller than the sum of its proper divisors (177477720).

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

81540840 is a wasteful number, since it uses less digits than its factorization.

81540840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40002 (or 39998 counting only the distinct ones).

The product of its (nonzero) digits is 5120, while the sum is 30.

The square root of 81540840 is about 9029.9966777403. The cubic root of 81540840 is about 433.6357310687.

The spelling of 81540840 in words is "eighty-one million, five hundred forty thousand, eight hundred forty".