209887613981 has 4 divisors (see below), whose sum is σ = 209893511100. Its totient is φ = 209881716864.

The previous prime is 209887613963. The next prime is 209887613989. The reversal of 209887613981 is 189316788902.

209887613981 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.

It can be written as a sum of positive squares in 2 ways, for example, as 160687937881 + 49199676100 = 400859^2 + 221810^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-209887613981 is a prime.

It is a super-2 number, since 2×209887613981² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209887613989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2894846 + ... + 2966463.

It is an arithmetic number, because the mean of its divisors is an integer number (52473377775).

Almost surely, 2^209887613981 is an apocalyptic number.

It is an amenable number.

209887613981 is a deficient number, since it is larger than the sum of its proper divisors (5897119).

209887613981 is an equidigital number, since it uses as much as digits as its factorization.

209887613981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5897118.

The product of its (nonzero) digits is 10450944, while the sum is 62.

The spelling of 209887613981 in words is "two hundred nine billion, eight hundred eighty-seven million, six hundred thirteen thousand, nine hundred eighty-one".