1221302561 has 2 divisors, whose sum is σ = 1221302562. Its totient is φ = 1221302560.

The previous prime is 1221302543. The next prime is 1221302591. The reversal of 1221302561 is 1652031221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1156000000 + 65302561 = 34000^2 + 8081^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221302561 - 2¹⁰ = 1221301537 is a prime.

It is not a weakly prime, because it can be changed into another prime (1221302591) 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, 610651280 + 610651281.

It is an arithmetic number, because the mean of its divisors is an integer number (610651281).

Almost surely, 2^1221302561 is an apocalyptic number.

It is an amenable number.

1221302561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221302561 is an equidigital number, since it uses as much as digits as its factorization.

1221302561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 1221302561 is about 34947.1395252888. The cubic root of 1221302561 is about 1068.9098749875.

Adding to 1221302561 its reverse (1652031221), we get a palindrome (2873333782).

The spelling of 1221302561 in words is "one billion, two hundred twenty-one million, three hundred two thousand, five hundred sixty-one".