1216320209 has 12 divisors (see below), whose sum is σ = 1329183900. Its totient is φ = 1112439744.

The previous prime is 1216320187. The next prime is 1216320221. The reversal of 1216320209 is 9020236121.

It can be written as a sum of positive squares in 6 ways, for example, as 428283025 + 788037184 = 20695^2 + 28072^2 .

It is not a de Polignac number, because 1216320209 - 2⁸ = 1216319953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1216320229) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14594 + ... + 51435.

It is an arithmetic number, because the mean of its divisors is an integer number (110765325).

Almost surely, 2^1216320209 is an apocalyptic number.

It is an amenable number.

1216320209 is a deficient number, since it is larger than the sum of its proper divisors (112863691).

1216320209 is a wasteful number, since it uses less digits than its factorization.

1216320209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66164 (or 66151 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 1216320209 is about 34875.7825575284. The cubic root of 1216320209 is about 1067.4543405452.

The spelling of 1216320209 in words is "one billion, two hundred sixteen million, three hundred twenty thousand, two hundred nine".