209891 has 4 divisors (see below), whose sum is σ = 228984. Its totient is φ = 190800.

The previous prime is 209887. The next prime is 209917. The reversal of 209891 is 198902.

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 209891 - 2² = 209887 is a prime.

It is a Duffinian number.

It is a zygodrome in base 2.

It is not an unprimeable number, because it can be changed into a prime (209801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9530 + ... + 9551.

It is an arithmetic number, because the mean of its divisors is an integer number (57246).

2²⁰⁹⁸⁹¹ is an apocalyptic number.

209891 is a deficient number, since it is larger than the sum of its proper divisors (19093).

209891 is a wasteful number, since it uses less digits than its factorization.

209891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19092.

The product of its (nonzero) digits is 1296, while the sum is 29.

The square root of 209891 is about 458.1386253090. The cubic root of 209891 is about 59.4289338194.

The spelling of 209891 in words is "two hundred nine thousand, eight hundred ninety-one".