1221816961 has 2 divisors, whose sum is σ = 1221816962. Its totient is φ = 1221816960.

The previous prime is 1221816949. The next prime is 1221816991. The reversal of 1221816961 is 1696181221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1153009936 + 68807025 = 33956^2 + 8295^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221816961 - 2⁵ = 1221816929 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1221816961.

It is not a weakly prime, because it can be changed into another prime (1221816991) 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, 610908480 + 610908481.

It is an arithmetic number, because the mean of its divisors is an integer number (610908481).

Almost surely, 2^1221816961 is an apocalyptic number.

It is an amenable number.

1221816961 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221816961 is an equidigital number, since it uses as much as digits as its factorization.

1221816961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 37.

The square root of 1221816961 is about 34954.4984372541. The cubic root of 1221816961 is about 1069.0599251822.

The spelling of 1221816961 in words is "one billion, two hundred twenty-one million, eight hundred sixteen thousand, nine hundred sixty-one".