1216220321 has 2 divisors, whose sum is σ = 1216220322. Its totient is φ = 1216220320.

The previous prime is 1216220311. The next prime is 1216220329. The reversal of 1216220321 is 1230226121.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1045552225 + 170668096 = 32335^2 + 13064^2 .

It is a cyclic number.

It is not a de Polignac number, because 1216220321 - 2¹⁰ = 1216219297 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1216220293 and 1216220302.

It is not a weakly prime, because it can be changed into another prime (1216220329) 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, 608110160 + 608110161.

It is an arithmetic number, because the mean of its divisors is an integer number (608110161).

Almost surely, 2^1216220321 is an apocalyptic number.

It is an amenable number.

1216220321 is a deficient number, since it is larger than the sum of its proper divisors (1).

1216220321 is an equidigital number, since it uses as much as digits as its factorization.

1216220321 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 1216220321 is about 34874.3504742382. The cubic root of 1216220321 is about 1067.4251188546.

Adding to 1216220321 its reverse (1230226121), we get a palindrome (2446446442).

The spelling of 1216220321 in words is "one billion, two hundred sixteen million, two hundred twenty thousand, three hundred twenty-one".