209728138 has 4 divisors (see below), whose sum is σ = 314592210. Its totient is φ = 104864068.

The previous prime is 209728109. The next prime is 209728153. The reversal of 209728138 is 831827902.

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., 174953529 + 34774609 = 13227^2 + 5897^2 .

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 209728138.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 52432033 + ... + 52432036.

Almost surely, 2^209728138 is an apocalyptic number.

209728138 is a deficient number, since it is larger than the sum of its proper divisors (104864072).

209728138 is a wasteful number, since it uses less digits than its factorization.

209728138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104864071.

The product of its (nonzero) digits is 48384, while the sum is 40.

The square root of 209728138 is about 14481.9935782336. The cubic root of 209728138 is about 594.1355882402.

The spelling of 209728138 in words is "two hundred nine million, seven hundred twenty-eight thousand, one hundred thirty-eight".