1221211809 has 24 divisors (see below), whose sum is σ = 1849891680. Its totient is φ = 804979296.

The previous prime is 1221211801. The next prime is 1221211867. The reversal of 1221211809 is 9081121221.

It is not a de Polignac number, because 1221211809 - 2³ = 1221211801 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (1221211801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6607 + ... + 49860.

It is an arithmetic number, because the mean of its divisors is an integer number (77078820).

Almost surely, 2^1221211809 is an apocalyptic number.

It is an amenable number.

1221211809 is a deficient number, since it is larger than the sum of its proper divisors (628679871).

1221211809 is an frugal number, since it uses more digits than its factorization.

1221211809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56571 (or 56559 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 27.

The square root of 1221211809 is about 34945.8410830245. The cubic root of 1221211809 is about 1068.8833983074.

The spelling of 1221211809 in words is "one billion, two hundred twenty-one million, two hundred eleven thousand, eight hundred nine".