221564 has 24 divisors (see below), whose sum is σ = 456288. Its totient is φ = 92160.

The previous prime is 221549. The next prime is 221567. The reversal of 221564 is 465122.

221564 = T₈₁ + T₈₂ + ... + T₁₂₂.

It is a happy number.

It is a plaindrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221567) by changing a digit.

221564 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1052 + ... + 1244.

It is an arithmetic number, because the mean of its divisors is an integer number (19012).

2²²¹⁵⁶⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 221564, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (228144).

221564 is an abundant number, since it is smaller than the sum of its proper divisors (234724).

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

221564 is a wasteful number, since it uses less digits than its factorization.

221564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 245 (or 243 counting only the distinct ones).

The product of its digits is 480, while the sum is 20.

The square root of 221564 is about 470.7058529485. The cubic root of 221564 is about 60.5108238267.

Adding to 221564 its reverse (465122), we get a palindrome (686686).

The spelling of 221564 in words is "two hundred twenty-one thousand, five hundred sixty-four".