1221708709 has 4 divisors (see below), whose sum is σ = 1315686316. Its totient is φ = 1127731104.

The previous prime is 1221708703. The next prime is 1221708713. The reversal of 1221708709 is 9078071221.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9078071221 = 557 ⋅16298153.

It can be written as a sum of positive squares in 2 ways, for example, as 246395809 + 975312900 = 15697^2 + 31230^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221708709 - 2⁹ = 1221708197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221708703) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 46988784 + ... + 46988809.

It is an arithmetic number, because the mean of its divisors is an integer number (328921579).

Almost surely, 2^1221708709 is an apocalyptic number.

It is an amenable number.

1221708709 is a deficient number, since it is larger than the sum of its proper divisors (93977607).

1221708709 is an equidigital number, since it uses as much as digits as its factorization.

1221708709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93977606.

The product of its (nonzero) digits is 14112, while the sum is 37.

The square root of 1221708709 is about 34952.9499327310. The cubic root of 1221708709 is about 1069.0283516332.

The spelling of 1221708709 in words is "one billion, two hundred twenty-one million, seven hundred eight thousand, seven hundred nine".