209139806 has 8 divisors (see below), whose sum is σ = 314035704. Its totient is φ = 104461240.

The previous prime is 209139803. The next prime is 209139839. The reversal of 209139806 is 608931902.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 209139806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209139803) 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, 51905 + ... + 55788.

It is an arithmetic number, because the mean of its divisors is an integer number (39254463).

Almost surely, 2^209139806 is an apocalyptic number.

209139806 is a deficient number, since it is larger than the sum of its proper divisors (104895898).

209139806 is a wasteful number, since it uses less digits than its factorization.

209139806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 108666.

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 209139806 is about 14461.6667780723. Note that the first 3 decimals coincide. The cubic root of 209139806 is about 593.5795090772.

The spelling of 209139806 in words is "two hundred nine million, one hundred thirty-nine thousand, eight hundred six".