231221809 has 16 divisors (see below), whose sum is σ = 287203840. Its totient is φ = 181258560.

The previous prime is 231221801. The next prime is 231221827. The reversal of 231221809 is 908122132.

It is not a de Polignac number, because 231221809 - 2³ = 231221801 is a prime.

It is not an unprimeable number, because it can be changed into a prime (231221801) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1737 + ... + 21574.

It is an arithmetic number, because the mean of its divisors is an integer number (17950240).

Almost surely, 2^231221809 is an apocalyptic number.

It is an amenable number.

231221809 is a deficient number, since it is larger than the sum of its proper divisors (55982031).

231221809 is a wasteful number, since it uses less digits than its factorization.

231221809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23440.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 231221809 is about 15205.9793831243. The cubic root of 231221809 is about 613.7755698839.

The spelling of 231221809 in words is "two hundred thirty-one million, two hundred twenty-one thousand, eight hundred nine".