209128 has 8 divisors (see below), whose sum is σ = 392130. Its totient is φ = 104560.

The previous prime is 209123. The next prime is 209147. The reversal of 209128 is 821902.

It can be written as a sum of positive squares in only one way, i.e., 161604 + 47524 = 402^2 + 218^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a junction number, because it is equal to n+sod(n) for n = 209099 and 209108.

It is not an unprimeable number, because it can be changed into a prime (209123) by changing a digit.

209128 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 13063 + ... + 13078.

2²⁰⁹¹²⁸ is an apocalyptic number.

It is an amenable number.

209128 is a deficient number, since it is larger than the sum of its proper divisors (183002).

209128 is a wasteful number, since it uses less digits than its factorization.

209128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26147 (or 26143 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 209128 is about 457.3051497633. The cubic root of 209128 is about 59.3568339624.

The spelling of 209128 in words is "two hundred nine thousand, one hundred twenty-eight".