81821200 has 60 divisors (see below), whose sum is σ = 199964880. Its totient is φ = 32164480.

The previous prime is 81821197. The next prime is 81821213. The reversal of 81821200 is 212818.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 21867 + ... + 25333.

It is an arithmetic number, because the mean of its divisors is an integer number (3332748).

Almost surely, 2^81821200 is an apocalyptic number.

81821200 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81821200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (99982440).

81821200 is an abundant number, since it is smaller than the sum of its proper divisors (118143680).

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

81821200 is a wasteful number, since it uses less digits than its factorization.

81821200 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3544 (or 3533 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 22.

The square root of 81821200 is about 9045.5071720717. The cubic root of 81821200 is about 434.1321491579.

The spelling of 81821200 in words is "eighty-one million, eight hundred twenty-one thousand, two hundred".