231721913 has 4 divisors (see below), whose sum is σ = 234325620. Its totient is φ = 229118208.

The previous prime is 231721879. The next prime is 231721921. The reversal of 231721913 is 319127132.

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 51437584 + 180284329 = 7172^2 + 13427^2 .

It is a cyclic number.

It is not a de Polignac number, because 231721913 - 2¹² = 231717817 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (231721013) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1301720 + ... + 1301897.

It is an arithmetic number, because the mean of its divisors is an integer number (58581405).

Almost surely, 2^231721913 is an apocalyptic number.

It is an amenable number.

231721913 is a deficient number, since it is larger than the sum of its proper divisors (2603707).

231721913 is an equidigital number, since it uses as much as digits as its factorization.

231721913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2603706.

The product of its digits is 2268, while the sum is 29.

The square root of 231721913 is about 15222.4148215715. The cubic root of 231721913 is about 614.2177579645.

The spelling of 231721913 in words is "two hundred thirty-one million, seven hundred twenty-one thousand, nine hundred thirteen".