208172609 has 6 divisors (see below), whose sum is σ = 217617666. Its totient is φ = 199121120.

The previous prime is 208172593. The next prime is 208172611. The reversal of 208172609 is 906271802.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 177955600 + 30217009 = 13340^2 + 5497^2 .

It is not a de Polignac number, because 208172609 - 2⁴ = 208172593 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (208172659) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 196232 + ... + 197289.

It is an arithmetic number, because the mean of its divisors is an integer number (36269611).

Almost surely, 2^208172609 is an apocalyptic number.

It is an amenable number.

208172609 is a deficient number, since it is larger than the sum of its proper divisors (9445057).

208172609 is an equidigital number, since it uses as much as digits as its factorization.

208172609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 393567 (or 393544 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 208172609 is about 14428.1880012703. The cubic root of 208172609 is about 592.6630637135.

The spelling of 208172609 in words is "two hundred eight million, one hundred seventy-two thousand, six hundred nine".