221655 has 16 divisors (see below), whose sum is σ = 405504. Its totient is φ = 101280.

The previous prime is 221653. The next prime is 221657. The reversal of 221655 is 556122.

It is an interprime number because it is at equal distance from previous prime (221653) and next prime (221657).

It is not a de Polignac number, because 221655 - 2¹ = 221653 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

221655 is a lucky number.

It is a nialpdrome in base 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 951 + ... + 1160.

It is an arithmetic number, because the mean of its divisors is an integer number (25344).

2²²¹⁶⁵⁵ is an apocalyptic number.

221655 is a deficient number, since it is larger than the sum of its proper divisors (183849).

221655 is a wasteful number, since it uses less digits than its factorization.

221655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2126.

The product of its digits is 600, while the sum is 21.

The square root of 221655 is about 470.8025063655. The cubic root of 221655 is about 60.5191069582.

Adding to 221655 its reverse (556122), we get a palindrome (777777).

The spelling of 221655 in words is "two hundred twenty-one thousand, six hundred fifty-five".