205781891 has 4 divisors (see below), whose sum is σ = 235179312. Its totient is φ = 176384472.

The previous prime is 205781887. The next prime is 205781921. The reversal of 205781891 is 198187502.

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 205781891 - 2² = 205781887 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (205781831) 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, 14698700 + ... + 14698713.

It is an arithmetic number, because the mean of its divisors is an integer number (58794828).

Almost surely, 2^205781891 is an apocalyptic number.

205781891 is a deficient number, since it is larger than the sum of its proper divisors (29397421).

205781891 is an equidigital number, since it uses as much as digits as its factorization.

205781891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29397420.

The product of its (nonzero) digits is 40320, while the sum is 41.

The square root of 205781891 is about 14345.0998950861. The cubic root of 205781891 is about 590.3855480580.

The spelling of 205781891 in words is "two hundred five million, seven hundred eighty-one thousand, eight hundred ninety-one".