209671987691 has 16 divisors (see below), whose sum is σ = 216307728384. Its totient is φ = 203117289984.

The previous prime is 209671987633. The next prime is 209671987697. The reversal of 209671987691 is 196789176902.

209671987691 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 209671987691 - 2¹⁸ = 209671725547 is a prime.

It is a super-2 number, since 2×209671987691² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (209671987697) 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 15 ways as a sum of consecutive naturals, for example, 30048395 + ... + 30055371.

It is an arithmetic number, because the mean of its divisors is an integer number (13519233024).

Almost surely, 2^209671987691 is an apocalyptic number.

209671987691 is a deficient number, since it is larger than the sum of its proper divisors (6635740693).

209671987691 is a wasteful number, since it uses less digits than its factorization.

209671987691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12650.

The product of its (nonzero) digits is 20575296, while the sum is 65.

The spelling of 209671987691 in words is "two hundred nine billion, six hundred seventy-one million, nine hundred eighty-seven thousand, six hundred ninety-one".