1221305809 has 8 divisors (see below), whose sum is σ = 1225707840. Its totient is φ = 1216911696.

The previous prime is 1221305801. The next prime is 1221305843. The reversal of 1221305809 is 9085031221.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1221305809 - 2³ = 1221305801 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221305801) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 544839 + ... + 547075.

It is an arithmetic number, because the mean of its divisors is an integer number (153213480).

Almost surely, 2^1221305809 is an apocalyptic number.

It is an amenable number.

1221305809 is a deficient number, since it is larger than the sum of its proper divisors (4402031).

1221305809 is a wasteful number, since it uses less digits than its factorization.

1221305809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3959.

The product of its (nonzero) digits is 4320, while the sum is 31.

The square root of 1221305809 is about 34947.1859954418. The cubic root of 1221305809 is about 1068.9108225595.

The spelling of 1221305809 in words is "one billion, two hundred twenty-one million, three hundred five thousand, eight hundred nine".