209245891 has 4 divisors (see below), whose sum is σ = 212369032. Its totient is φ = 206122752.

The previous prime is 209245859. The next prime is 209245903. The reversal of 209245891 is 198542902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 198542902 = 2 ⋅99271451.

It is a cyclic number.

It is not a de Polignac number, because 209245891 - 2⁵ = 209245859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (209245811) 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, 1561470 + ... + 1561603.

It is an arithmetic number, because the mean of its divisors is an integer number (53092258).

Almost surely, 2^209245891 is an apocalyptic number.

209245891 is a deficient number, since it is larger than the sum of its proper divisors (3123141).

209245891 is an equidigital number, since it uses as much as digits as its factorization.

209245891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3123140.

The product of its (nonzero) digits is 51840, while the sum is 40.

The square root of 209245891 is about 14465.3341129751. The cubic root of 209245891 is about 593.6798554107.

The spelling of 209245891 in words is "two hundred nine million, two hundred forty-five thousand, eight hundred ninety-one".