221721220 has 48 divisors (see below), whose sum is σ = 538570368. Its totient is φ = 75098880.

The previous prime is 221721217. The next prime is 221721251. The reversal of 221721220 is 22127122.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 2080 + ... + 21160.

It is an arithmetic number, because the mean of its divisors is an integer number (11220216).

Almost surely, 2^221721220 is an apocalyptic number.

221721220 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 221721220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (269285184).

221721220 is an abundant number, since it is smaller than the sum of its proper divisors (316849148).

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

221721220 is a wasteful number, since it uses less digits than its factorization.

221721220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19180 (or 19178 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 19.

The square root of 221721220 is about 14890.3062426533. The cubic root of 221721220 is about 605.2513310434.

Adding to 221721220 its reverse (22127122), we get a palindrome (243848342).

The spelling of 221721220 in words is "two hundred twenty-one million, seven hundred twenty-one thousand, two hundred twenty".