1231331221 has 2 divisors, whose sum is σ = 1231331222. Its totient is φ = 1231331220.

The previous prime is 1231331201. The next prime is 1231331263. The reversal of 1231331221 is 1221331321.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1002988900 + 228342321 = 31670^2 + 15111^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1231331221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1231331201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 615665610 + 615665611.

It is an arithmetic number, because the mean of its divisors is an integer number (615665611).

Almost surely, 2^1231331221 is an apocalyptic number.

It is an amenable number.

1231331221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1231331221 is an equidigital number, since it uses as much as digits as its factorization.

1231331221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 216, while the sum is 19.

The square root of 1231331221 is about 35090.3294512890. The cubic root of 1231331221 is about 1071.8276682979.

Adding to 1231331221 its reverse (1221331321), we get a palindrome (2452662542).

It can be divided in two parts, 12313 and 31221, that added together give a palindrome (43534).

The spelling of 1231331221 in words is "one billion, two hundred thirty-one million, three hundred thirty-one thousand, two hundred twenty-one".