221312231 has 4 divisors (see below), whose sum is σ = 252928272. Its totient is φ = 189696192.

The previous prime is 221312191. The next prime is 221312243. The reversal of 221312231 is 132213122.

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

It is not a de Polignac number, because 221312231 - 2⁶ = 221312167 is a prime.

It is a super-2 number, since 2×221312231² = 97958207180394722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221312251) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15808010 + ... + 15808023.

It is an arithmetic number, because the mean of its divisors is an integer number (63232068).

Almost surely, 2^221312231 is an apocalyptic number.

221312231 is a deficient number, since it is larger than the sum of its proper divisors (31616041).

221312231 is an equidigital number, since it uses as much as digits as its factorization.

221312231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31616040.

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

The square root of 221312231 is about 14876.5665057499. The cubic root of 221312231 is about 604.8789512619.

Adding to 221312231 its reverse (132213122), we get a palindrome (353525353).

The spelling of 221312231 in words is "two hundred twenty-one million, three hundred twelve thousand, two hundred thirty-one".