1216336721 has 2 divisors, whose sum is σ = 1216336722. Its totient is φ = 1216336720.

The previous prime is 1216336711. The next prime is 1216336741. The reversal of 1216336721 is 1276336121.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1174021696 + 42315025 = 34264^2 + 6505^2 .

It is an emirp because it is prime and its reverse (1276336121) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1216336721 - 2¹⁸ = 1216074577 is a prime.

It is not a weakly prime, because it can be changed into another prime (1216336711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 608168360 + 608168361.

It is an arithmetic number, because the mean of its divisors is an integer number (608168361).

Almost surely, 2^1216336721 is an apocalyptic number.

It is an amenable number.

1216336721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1216336721 is an equidigital number, since it uses as much as digits as its factorization.

1216336721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9072, while the sum is 32.

The square root of 1216336721 is about 34876.0192825959. The cubic root of 1216336721 is about 1067.4591708868.

It can be divided in two parts, 12163 and 36721, that added together give a palindrome (48884).

The spelling of 1216336721 in words is "one billion, two hundred sixteen million, three hundred thirty-six thousand, seven hundred twenty-one".