1311131221 has 2 divisors, whose sum is σ = 1311131222. Its totient is φ = 1311131220.

The previous prime is 1311131167. The next prime is 1311131281. The reversal of 1311131221 is 1221311131.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 975875121 + 335256100 = 31239^2 + 18310^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1311131221 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1311131195 and 1311131204.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1311131281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 655565610 + 655565611.

It is an arithmetic number, because the mean of its divisors is an integer number (655565611).

Almost surely, 2^1311131221 is an apocalyptic number.

It is an amenable number.

1311131221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1311131221 is an equidigital number, since it uses as much as digits as its factorization.

1311131221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36, while the sum is 16.

The square root of 1311131221 is about 36209.5459927351. The cubic root of 1311131221 is about 1094.4990434535.

Adding to 1311131221 its reverse (1221311131), we get a palindrome (2532442352).

The spelling of 1311131221 in words is "one billion, three hundred eleven million, one hundred thirty-one thousand, two hundred twenty-one".