1221312173 has 2 divisors, whose sum is σ = 1221312174. Its totient is φ = 1221312172.

The previous prime is 1221312151. The next prime is 1221312199. The reversal of 1221312173 is 3712131221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 787756489 + 433555684 = 28067^2 + 20822^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221312173 - 2¹⁰ = 1221311149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221312073) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610656086 + 610656087.

It is an arithmetic number, because the mean of its divisors is an integer number (610656087).

Almost surely, 2^1221312173 is an apocalyptic number.

It is an amenable number.

1221312173 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221312173 is an equidigital number, since it uses as much as digits as its factorization.

1221312173 is an evil number, because the sum of its binary digits is even.

The product of its digits is 504, while the sum is 23.

The square root of 1221312173 is about 34947.2770470032. The cubic root of 1221312173 is about 1068.9126791888.

Adding to 1221312173 its reverse (3712131221), we get a palindrome (4933443394).

The spelling of 1221312173 in words is "one billion, two hundred twenty-one million, three hundred twelve thousand, one hundred seventy-three".