209043891 has 12 divisors (see below), whose sum is σ = 345088432. Its totient is φ = 119453616.

The previous prime is 209043859. The next prime is 209043899. The reversal of 209043891 is 198340902.

It is not a de Polignac number, because 209043891 - 2⁵ = 209043859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (209043899) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1659016 + ... + 1659141.

Almost surely, 2^209043891 is an apocalyptic number.

209043891 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

209043891 is a deficient number, since it is larger than the sum of its proper divisors (136044541).

209043891 is a wasteful number, since it uses less digits than its factorization.

209043891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3318170 (or 3318167 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 209043891 is about 14458.3502170891. The cubic root of 209043891 is about 593.4887533838.

The spelling of 209043891 in words is "two hundred nine million, forty-three thousand, eight hundred ninety-one".