1216551409 has 2 divisors, whose sum is σ = 1216551410. Its totient is φ = 1216551408.

The previous prime is 1216551403. The next prime is 1216551439. The reversal of 1216551409 is 9041556121.

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., 699443809 + 517107600 = 26447^2 + 22740^2 .

It is a cyclic number.

It is not a de Polignac number, because 1216551409 - 2⁵ = 1216551377 is a prime.

It is not a weakly prime, because it can be changed into another prime (1216551403) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 608275704 + 608275705.

It is an arithmetic number, because the mean of its divisors is an integer number (608275705).

Almost surely, 2^1216551409 is an apocalyptic number.

It is an amenable number.

1216551409 is a deficient number, since it is larger than the sum of its proper divisors (1).

1216551409 is an equidigital number, since it uses as much as digits as its factorization.

1216551409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10800, while the sum is 34.

The square root of 1216551409 is about 34879.0970209953. The cubic root of 1216551409 is about 1067.5219707098.

The spelling of 1216551409 in words is "one billion, two hundred sixteen million, five hundred fifty-one thousand, four hundred nine".