231097991 has 4 divisors (see below), whose sum is σ = 231325800. Its totient is φ = 230870184.

The previous prime is 231097981. The next prime is 231098003. The reversal of 231097991 is 199790132.

231097991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is not a de Polignac number, because 231097991 - 2⁶ = 231097927 is a prime.

It is a Duffinian number.

It is a zygodrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (231097981) 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, 112376 + ... + 114413.

It is an arithmetic number, because the mean of its divisors is an integer number (57831450).

Almost surely, 2^231097991 is an apocalyptic number.

231097991 is a deficient number, since it is larger than the sum of its proper divisors (227809).

231097991 is a wasteful number, since it uses less digits than its factorization.

231097991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 227808.

The product of its (nonzero) digits is 30618, while the sum is 41.

The square root of 231097991 is about 15201.9074789975. The cubic root of 231097991 is about 613.6659925144.

The spelling of 231097991 in words is "two hundred thirty-one million, ninety-seven thousand, nine hundred ninety-one".