1231331209 has 4 divisors (see below), whose sum is σ = 1246917760. Its totient is φ = 1215744660.

The previous prime is 1231331201. The next prime is 1231331221. The reversal of 1231331209 is 9021331321.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 9021331321 = 179 ⋅50398499.

It is a cyclic number.

It is not a de Polignac number, because 1231331209 - 2³ = 1231331201 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1231331201) 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, 7793157 + ... + 7793314.

It is an arithmetic number, because the mean of its divisors is an integer number (311729440).

Almost surely, 2^1231331209 is an apocalyptic number.

It is an amenable number.

1231331209 is a deficient number, since it is larger than the sum of its proper divisors (15586551).

1231331209 is an equidigital number, since it uses as much as digits as its factorization.

1231331209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15586550.

The product of its (nonzero) digits is 972, while the sum is 25.

The square root of 1231331209 is about 35090.3292803017. The cubic root of 1231331209 is about 1071.8276648160.

The spelling of 1231331209 in words is "one billion, two hundred thirty-one million, three hundred thirty-one thousand, two hundred nine".