81221205000 has 320 divisors, whose sum is σ = 279945388800. Its totient is φ = 19503360000.

The previous prime is 81221204983. The next prime is 81221205083. The reversal of 81221205000 is 50212218.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 7989921 + ... + 8000079.

It is an arithmetic number, because the mean of its divisors is an integer number (874829340).

Almost surely, 2^81221205000 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81221205000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (139972694400).

81221205000 is an abundant number, since it is smaller than the sum of its proper divisors (198724183800).

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

81221205000 is a wasteful number, since it uses less digits than its factorization.

81221205000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10242 (or 10223 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 21.

Adding to 81221205000 its reverse (50212218), we get a palindrome (81271417218).

The spelling of 81221205000 in words is "eighty-one billion, two hundred twenty-one million, two hundred five thousand".