221205660 has 96 divisors (see below), whose sum is σ = 683387712. Its totient is φ = 53114880.

The previous prime is 221205637. The next prime is 221205661. The reversal of 221205660 is 66502122.

It is a self number, because there is not a number n which added to its sum of digits gives 221205660.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221205661) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 28522 + ... + 35438.

It is an arithmetic number, because the mean of its divisors is an integer number (7118622).

Almost surely, 2^221205660 is an apocalyptic number.

221205660 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 221205660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (341693856).

221205660 is an abundant number, since it is smaller than the sum of its proper divisors (462182052).

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

221205660 is a wasteful number, since it uses less digits than its factorization.

221205660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6983 (or 6981 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 221205660 is about 14872.9842331659. The cubic root of 221205660 is about 604.7818442557.

Adding to 221205660 its reverse (66502122), we get a palindrome (287707782).

The spelling of 221205660 in words is "two hundred twenty-one million, two hundred five thousand, six hundred sixty".