221221312400 has 120 divisors (see below), whose sum is σ = 580442462400. Its totient is φ = 80355110400.

The previous prime is 221221312357. The next prime is 221221312421. The reversal of 221221312400 is 4213122122.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4016246 + ... + 4070954.

It is an arithmetic number, because the mean of its divisors is an integer number (4837020520).

Almost surely, 2^221221312400 is an apocalyptic number.

221221312400 is a gapful number since it is divisible by the number (20) 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 221221312400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (290221231200).

221221312400 is an abundant number, since it is smaller than the sum of its proper divisors (359221150000).

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

221221312400 is a wasteful number, since it uses less digits than its factorization.

221221312400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55657 (or 55646 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

Adding to 221221312400 its reverse (4213122122), we get a palindrome (225434434522).

The spelling of 221221312400 in words is "two hundred twenty-one billion, two hundred twenty-one million, three hundred twelve thousand, four hundred".