221213231 has 4 divisors (see below), whose sum is σ = 234225792. Its totient is φ = 208200672.

The previous prime is 221213221. The next prime is 221213233. The reversal of 221213231 is 132312122.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 221213231 - 2¹⁰ = 221212207 is a prime.

It is a super-2 number, since 2×221213231² = 97870587138918722, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (17), and also a Moran number because the ratio is a prime number: 13012543 = 221213231 / (2 + 2 + 1 + 2 + 1 + 3 + 2 + 3 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221213233) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6506255 + ... + 6506288.

It is an arithmetic number, because the mean of its divisors is an integer number (58556448).

Almost surely, 2^221213231 is an apocalyptic number.

221213231 is a deficient number, since it is larger than the sum of its proper divisors (13012561).

221213231 is a wasteful number, since it uses less digits than its factorization.

221213231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13012560.

The product of its digits is 144, while the sum is 17.

The square root of 221213231 is about 14873.2387528742. The cubic root of 221213231 is about 604.7887439452.

Adding to 221213231 its reverse (132312122), we get a palindrome (353525353).

It can be divided in two parts, 22121 and 3231, that added together give a palindrome (25352).

The spelling of 221213231 in words is "two hundred twenty-one million, two hundred thirteen thousand, two hundred thirty-one".