1221326817817 has 2 divisors, whose sum is σ = 1221326817818. Its totient is φ = 1221326817816.

The previous prime is 1221326817719. The next prime is 1221326817883. The reversal of 1221326817817 is 7187186231221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1053217797696 + 168109020121 = 1026264^2 + 410011^2 .

It is an emirp because it is prime and its reverse (7187186231221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221326817817 - 2³¹ = 1219179334169 is a prime.

It is not a weakly prime, because it can be changed into another prime (1221326817017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610663408908 + 610663408909.

It is an arithmetic number, because the mean of its divisors is an integer number (610663408909).

Almost surely, 2^{1221326817817} is an apocalyptic number.

It is an amenable number.

1221326817817 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221326817817 is an equidigital number, since it uses as much as digits as its factorization.

1221326817817 is an evil number, because the sum of its binary digits is even.

The product of its digits is 451584, while the sum is 49.

The spelling of 1221326817817 in words is "one trillion, two hundred twenty-one billion, three hundred twenty-six million, eight hundred seventeen thousand, eight hundred seventeen".