209906 has 4 divisors (see below), whose sum is σ = 314862. Its totient is φ = 104952.

The previous prime is 209887. The next prime is 209917. The reversal of 209906 is 609902.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 198025 + 11881 = 445^2 + 109^2 .

It is an unprimeable number.

209906 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 as a sum of consecutive naturals, namely, 52475 + ... + 52478.

2²⁰⁹⁹⁰⁶ is an apocalyptic number.

209906 is a deficient number, since it is larger than the sum of its proper divisors (104956).

209906 is a wasteful number, since it uses less digits than its factorization.

209906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104955.

The product of its (nonzero) digits is 972, while the sum is 26.

The square root of 209906 is about 458.1549956074. The cubic root of 209906 is about 59.4303494951.

The spelling of 209906 in words is "two hundred nine thousand, nine hundred six".