81811500 has 48 divisors (see below), whose sum is σ = 238239456. Its totient is φ = 21816000.

The previous prime is 81811447. The next prime is 81811517. The reversal of 81811500 is 511818.

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, 25771 + ... + 28770.

It is an arithmetic number, because the mean of its divisors is an integer number (4963322).

Almost surely, 2^81811500 is an apocalyptic number.

It is an amenable number.

81811500 is an abundant number, since it is smaller than the sum of its proper divisors (156427956).

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

81811500 is a wasteful number, since it uses less digits than its factorization.

81811500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54563 (or 54551 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 24.

The square root of 81811500 is about 9044.9709783946. The cubic root of 81811500 is about 434.1149928534.

The spelling of 81811500 in words is "eighty-one million, eight hundred eleven thousand, five hundred".