1216081813 has 2 divisors, whose sum is σ = 1216081814. Its totient is φ = 1216081812.

The previous prime is 1216081793. The next prime is 1216081817. The reversal of 1216081813 is 3181806121.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 638977284 + 577104529 = 25278^2 + 24023^2 .

It is a cyclic number.

It is not a de Polignac number, because 1216081813 - 2²¹ = 1213984661 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1216081817) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 608040906 + 608040907.

It is an arithmetic number, because the mean of its divisors is an integer number (608040907).

Almost surely, 2^1216081813 is an apocalyptic number.

It is an amenable number.

1216081813 is a deficient number, since it is larger than the sum of its proper divisors (1).

1216081813 is an equidigital number, since it uses as much as digits as its factorization.

1216081813 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 1216081813 is about 34872.3646029345. The cubic root of 1216081813 is about 1067.3845964458.

Adding to 1216081813 its reverse (3181806121), we get a palindrome (4397887934).

The spelling of 1216081813 in words is "one billion, two hundred sixteen million, eighty-one thousand, eight hundred thirteen".