231921209 has 4 divisors (see below), whose sum is σ = 249761316. Its totient is φ = 214081104.

The previous prime is 231921113. The next prime is 231921227. The reversal of 231921209 is 902129132.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 116035984 + 115885225 = 10772^2 + 10765^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-231921209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (231921299) 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, 8920034 + ... + 8920059.

It is an arithmetic number, because the mean of its divisors is an integer number (62440329).

Almost surely, 2^231921209 is an apocalyptic number.

It is an amenable number.

231921209 is a deficient number, since it is larger than the sum of its proper divisors (17840107).

231921209 is a wasteful number, since it uses less digits than its factorization.

231921209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17840106.

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 231921209 is about 15228.9595508032. The cubic root of 231921209 is about 614.3937966533.

The spelling of 231921209 in words is "two hundred thirty-one million, nine hundred twenty-one thousand, two hundred nine".