208971681 has 4 divisors (see below), whose sum is σ = 278628912. Its totient is φ = 139314452.

The previous prime is 208971677. The next prime is 208971683. The reversal of 208971681 is 186179802.

208971681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 208971681 - 2² = 208971677 is a prime.

It is a super-2 number, since 2×208971681² = 87338326919931522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (208971683) 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, 34828611 + ... + 34828616.

It is an arithmetic number, because the mean of its divisors is an integer number (69657228).

Almost surely, 2^208971681 is an apocalyptic number.

It is an amenable number.

208971681 is a deficient number, since it is larger than the sum of its proper divisors (69657231).

208971681 is an equidigital number, since it uses as much as digits as its factorization.

208971681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69657230.

The product of its (nonzero) digits is 48384, while the sum is 42.

The square root of 208971681 is about 14455.8528285259. The cubic root of 208971681 is about 593.4204092700.

It can be divided in two parts, 20897 and 1681, that added together give a triangular number (22578 = T₂₁₂).

The spelling of 208971681 in words is "two hundred eight million, nine hundred seventy-one thousand, six hundred eighty-one".