231720817 has 4 divisors (see below), whose sum is σ = 239711220. Its totient is φ = 223730416.

The previous prime is 231720809. The next prime is 231720869. The reversal of 231720817 is 718027132.

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 160757041 + 70963776 = 12679^2 + 8424^2 .

It is a cyclic number.

It is not a de Polignac number, because 231720817 - 2³ = 231720809 is a prime.

It is a super-2 number, since 2×231720817² = 107389074062294978, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (231720887) 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, 3995158 + ... + 3995215.

It is an arithmetic number, because the mean of its divisors is an integer number (59927805).

Almost surely, 2^231720817 is an apocalyptic number.

It is an amenable number.

231720817 is a deficient number, since it is larger than the sum of its proper divisors (7990403).

231720817 is an equidigital number, since it uses as much as digits as its factorization.

231720817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7990402.

The product of its (nonzero) digits is 4704, while the sum is 31.

The square root of 231720817 is about 15222.3788219844. The cubic root of 231720817 is about 614.2167895857.

Adding to 231720817 its reverse (718027132), we get a palindrome (949747949).

The spelling of 231720817 in words is "two hundred thirty-one million, seven hundred twenty thousand, eight hundred seventeen".