81221200 has 60 divisors (see below), whose sum is σ = 205423360. Its totient is φ = 30775680.

The previous prime is 81221197. The next prime is 81221201. The reversal of 81221200 is 212218.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81221201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2257 + ... + 12943.

Almost surely, 2^81221200 is an apocalyptic number.

81221200 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 81221200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (102711680).

81221200 is an abundant number, since it is smaller than the sum of its proper divisors (124202160).

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

81221200 is a wasteful number, since it uses less digits than its factorization.

81221200 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10724 (or 10713 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 16.

The square root of 81221200 is about 9012.2805105034. The cubic root of 81221200 is about 433.0683718818.

Adding to 81221200 its reverse (212218), we get a palindrome (81433418).

The spelling of 81221200 in words is "eighty-one million, two hundred twenty-one thousand, two hundred".