209851 has 2 divisors, whose sum is σ = 209852. Its totient is φ = 209850.

The previous prime is 209837. The next prime is 209857. The reversal of 209851 is 158902.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 209851 - 2⁵ = 209819 is a prime.

It is a plaindrome in base 16.

It is a zygodrome in base 16.

It is not a weakly prime, because it can be changed into another prime (209857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104925 + 104926.

It is an arithmetic number, because the mean of its divisors is an integer number (104926).

2²⁰⁹⁸⁵¹ is an apocalyptic number.

209851 is a deficient number, since it is larger than the sum of its proper divisors (1).

209851 is an equidigital number, since it uses as much as digits as its factorization.

209851 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 25.

The square root of 209851 is about 458.0949683199. The cubic root of 209851 is about 59.4251583544.

The spelling of 209851 in words is "two hundred nine thousand, eight hundred fifty-one".