221551 has 6 divisors (see below), whose sum is σ = 243656. Its totient is φ = 201300.

The previous prime is 221549. The next prime is 221567. The reversal of 221551 is 155122.

It is not a de Polignac number, because 221551 - 2¹ = 221549 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221581) 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 5 ways as a sum of consecutive naturals, for example, 795 + ... + 1036.

2²²¹⁵⁵¹ is an apocalyptic number.

221551 is the 211-st centered decagonal number.

221551 is a deficient number, since it is larger than the sum of its proper divisors (22105).

221551 is a wasteful number, since it uses less digits than its factorization.

221551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1853 (or 1842 counting only the distinct ones).

The product of its digits is 100, while the sum is 16.

The square root of 221551 is about 470.6920436974. The cubic root of 221551 is about 60.5096403371.

Adding to 221551 its reverse (155122), we get a palindrome (376673).

It can be divided in two parts, 221 and 551, that multiplied together give a triangular number (121771 = T₄₉₃).

The spelling of 221551 in words is "two hundred twenty-one thousand, five hundred fifty-one".