1219920809 has 4 divisors (see below), whose sum is σ = 1222318020. Its totient is φ = 1217523600.

The previous prime is 1219920781. The next prime is 1219920811. The reversal of 1219920809 is 9080299121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9080299121 = 43 ⋅211169747.

It can be written as a sum of positive squares in 2 ways, for example, as 367105600 + 852815209 = 19160^2 + 29203^2 .

It is a cyclic number.

It is not a de Polignac number, because 1219920809 - 2¹² = 1219916713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1219920839) 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, 1197842 + ... + 1198859.

It is an arithmetic number, because the mean of its divisors is an integer number (305579505).

Almost surely, 2^1219920809 is an apocalyptic number.

It is an amenable number.

1219920809 is a deficient number, since it is larger than the sum of its proper divisors (2397211).

1219920809 is an equidigital number, since it uses as much as digits as its factorization.

1219920809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2397210.

The product of its (nonzero) digits is 23328, while the sum is 41.

The square root of 1219920809 is about 34927.3647588821. The cubic root of 1219920809 is about 1068.5066099935.

The spelling of 1219920809 in words is "one billion, two hundred nineteen million, nine hundred twenty thousand, eight hundred nine".