1221001209 has 20 divisors (see below), whose sum is σ = 1824904576. Its totient is φ = 813581496.

The previous prime is 1221001189. The next prime is 1221001261. The reversal of 1221001209 is 9021001221.

It is not a de Polignac number, because 1221001209 - 2¹¹ = 1220999161 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 1221001191 and 1221001200.

It is not an unprimeable number, because it can be changed into a prime (1221003209) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 307692 + ... + 311634.

Almost surely, 2^1221001209 is an apocalyptic number.

It is an amenable number.

1221001209 is a deficient number, since it is larger than the sum of its proper divisors (603903367).

1221001209 is an equidigital number, since it uses as much as digits as its factorization.

1221001209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7778 (or 7769 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 18.

The square root of 1221001209 is about 34942.8277190041. The cubic root of 1221001209 is about 1068.8219512040.

The spelling of 1221001209 in words is "one billion, two hundred twenty-one million, one thousand, two hundred nine".