231811997 has 2 divisors, whose sum is σ = 231811998. Its totient is φ = 231811996.

The previous prime is 231811973. The next prime is 231811999. The reversal of 231811997 is 799118132.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 186841561 + 44970436 = 13669^2 + 6706^2 .

It is a cyclic number.

It is not a de Polignac number, because 231811997 - 2¹⁰ = 231810973 is a prime.

Together with 231811999, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (231811999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 115905998 + 115905999.

It is an arithmetic number, because the mean of its divisors is an integer number (115905999).

Almost surely, 2^231811997 is an apocalyptic number.

It is an amenable number.

231811997 is a deficient number, since it is larger than the sum of its proper divisors (1).

231811997 is an equidigital number, since it uses as much as digits as its factorization.

231811997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27216, while the sum is 41.

The square root of 231811997 is about 15225.3734601158. The cubic root of 231811997 is about 614.2973418979.

The spelling of 231811997 in words is "two hundred thirty-one million, eight hundred eleven thousand, nine hundred ninety-seven".