208666261861 has 4 divisors (see below), whose sum is σ = 213755682924. Its totient is φ = 203576840800.

The previous prime is 208666261823. The next prime is 208666261883. The reversal of 208666261861 is 168162666802.

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

It can be written as a sum of positive squares in 2 ways, for example, as 126064053025 + 82602208836 = 355055^2 + 287406^2 .

It is not a de Polignac number, because 208666261861 - 2¹⁷ = 208666130789 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 208666261799 and 208666261808.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (208666261061) 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, 2544710470 + ... + 2544710551.

It is an arithmetic number, because the mean of its divisors is an integer number (53438920731).

Almost surely, 2^208666261861 is an apocalyptic number.

It is an amenable number.

208666261861 is a deficient number, since it is larger than the sum of its proper divisors (5089421063).

208666261861 is an equidigital number, since it uses as much as digits as its factorization.

208666261861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5089421062.

The product of its (nonzero) digits is 1990656, while the sum is 52.

The spelling of 208666261861 in words is "two hundred eight billion, six hundred sixty-six million, two hundred sixty-one thousand, eight hundred sixty-one".