221544 has 48 divisors (see below), whose sum is σ = 638820. Its totient is φ = 69120.

The previous prime is 221539. The next prime is 221549. The reversal of 221544 is 445122.

It is an interprime number because it is at equal distance from previous prime (221539) and next prime (221549).

It can be written as a sum of positive squares in 2 ways, for example, as 213444 + 8100 = 462^2 + 90^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a plaindrome in base 13 and base 15.

It is not an unprimeable number, because it can be changed into a prime (221549) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1134 + ... + 1314.

2²²¹⁵⁴⁴ is an apocalyptic number.

221544 is a gapful number since it is divisible by the number (24) 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 221544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (319410).

221544 is an abundant number, since it is smaller than the sum of its proper divisors (417276).

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

221544 is a wasteful number, since it uses less digits than its factorization.

221544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210 (or 203 counting only the distinct ones).

The product of its digits is 320, while the sum is 18.

The square root of 221544 is about 470.6846077789. The cubic root of 221544 is about 60.5090030542.

Adding to 221544 its reverse (445122), we get a palindrome (666666).

The spelling of 221544 in words is "two hundred twenty-one thousand, five hundred forty-four".