1221805709 has 2 divisors, whose sum is σ = 1221805710. Its totient is φ = 1221805708.

The previous prime is 1221805693. The next prime is 1221805751. The reversal of 1221805709 is 9075081221.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 740003209 + 481802500 = 27203^2 + 21950^2 .

It is an emirp because it is prime and its reverse (9075081221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221805709 - 2⁴ = 1221805693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221805309) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610902854 + 610902855.

It is an arithmetic number, because the mean of its divisors is an integer number (610902855).

Almost surely, 2^1221805709 is an apocalyptic number.

It is an amenable number.

1221805709 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221805709 is an equidigital number, since it uses as much as digits as its factorization.

1221805709 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10080, while the sum is 35.

The square root of 1221805709 is about 34954.3374847815. The cubic root of 1221805709 is about 1069.0566434306.

The spelling of 1221805709 in words is "one billion, two hundred twenty-one million, eight hundred five thousand, seven hundred nine".