221213820 has 48 divisors (see below), whose sum is σ = 623226240. Its totient is φ = 58625856.

The previous prime is 221213813. The next prime is 221213831. The reversal of 221213820 is 28312122.

It is a happy number.

221213820 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

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 15 ways as a sum of consecutive naturals, for example, 1530 + ... + 21089.

It is an arithmetic number, because the mean of its divisors is an integer number (12983880).

Almost surely, 2^221213820 is an apocalyptic number.

221213820 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 221213820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (311613120).

221213820 is an abundant number, since it is smaller than the sum of its proper divisors (402012420).

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

221213820 is a wasteful number, since it uses less digits than its factorization.

221213820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22794 (or 22792 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 221213820 is about 14873.2585535248. The cubic root of 221213820 is about 604.7892807127.

Adding to 221213820 its reverse (28312122), we get a palindrome (249525942).

The spelling of 221213820 in words is "two hundred twenty-one million, two hundred thirteen thousand, eight hundred twenty".