31223221 has 4 divisors (see below), whose sum is σ = 31234444. Its totient is φ = 31212000.

The previous prime is 31223219. The next prime is 31223239. The reversal of 31223221 is 12232213.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 1028196 + 30195025 = 1014^2 + 5495^2 .

It is a 3-Lehmer number, since φ(31223221) divides (31223221-1)³.

It is a cyclic number.

It is not a de Polignac number, because 31223221 - 2¹ = 31223219 is a prime.

It is a super-2 number, since 2×31223221² = 1949779059229682, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 31223195 and 31223204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31223261) 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, 2041 + ... + 8161.

It is an arithmetic number, because the mean of its divisors is an integer number (7808611).

Almost surely, 2^31223221 is an apocalyptic number.

It is an amenable number.

31223221 is a deficient number, since it is larger than the sum of its proper divisors (11223).

31223221 is an equidigital number, since it uses as much as digits as its factorization.

31223221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11222.

The product of its digits is 144, while the sum is 16.

The square root of 31223221 is about 5587.7742438291. The cubic root of 31223221 is about 314.8902649596.

Adding to 31223221 its reverse (12232213), we get a palindrome (43455434).

It can be divided in two parts, 3 and 1223221, that multiplied together give a palindrome (3669663).

The spelling of 31223221 in words is "thirty-one million, two hundred twenty-three thousand, two hundred twenty-one".