205317691 has 2 divisors, whose sum is σ = 205317692. Its totient is φ = 205317690.

The previous prime is 205317689. The next prime is 205317713. The reversal of 205317691 is 196713502.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 205317691 - 2¹ = 205317689 is a prime.

Together with 205317689, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (205317631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102658845 + 102658846.

It is an arithmetic number, because the mean of its divisors is an integer number (102658846).

Almost surely, 2^205317691 is an apocalyptic number.

205317691 is a deficient number, since it is larger than the sum of its proper divisors (1).

205317691 is an equidigital number, since it uses as much as digits as its factorization.

205317691 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11340, while the sum is 34.

The square root of 205317691 is about 14328.9110193343. The cubic root of 205317691 is about 589.9412859316.

It can be divided in two parts, 20 and 5317691, that multiplied together give a triangular number (106353820 = T₁₄₅₈₄).

The spelling of 205317691 in words is "two hundred five million, three hundred seventeen thousand, six hundred ninety-one".