208509981 has 8 divisors (see below), whose sum is σ = 294367104. Its totient is φ = 130829760.

The previous prime is 208509923. The next prime is 208510013. The reversal of 208509981 is 189905802.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 208509981 - 2¹⁹ = 207985693 is a prime.

It is a super-2 number, since 2×208509981² = 86952824353240722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (208504981) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2044165 + ... + 2044266.

It is an arithmetic number, because the mean of its divisors is an integer number (36795888).

Almost surely, 2^208509981 is an apocalyptic number.

It is an amenable number.

208509981 is a deficient number, since it is larger than the sum of its proper divisors (85857123).

208509981 is a wasteful number, since it uses less digits than its factorization.

208509981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4088451.

The product of its (nonzero) digits is 51840, while the sum is 42.

The square root of 208509981 is about 14439.8746878219. The cubic root of 208509981 is about 592.9830545887.

The spelling of 208509981 in words is "two hundred eight million, five hundred nine thousand, nine hundred eighty-one".