261839960209 has 3 divisors (see below), whose sum is σ = 261840471913. Its totient is φ = 261839448506.

The previous prime is 261839960167. The next prime is 261839960237. The reversal of 261839960209 is 902069938162.

It is a happy number.

The square root of 261839960209 is 511703.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 261839960209 - 2²⁹ = 261303089297 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 261839960209.

It is not an unprimeable number, because it can be changed into a prime (261839960309) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 255852 + ... + 767554.

Almost surely, 2^261839960209 is an apocalyptic number.

261839960209 is the 511703-rd square number.

261839960209 is the 255852-nd centered octagonal number.

It is an amenable number.

261839960209 is a deficient number, since it is larger than the sum of its proper divisors (511704).

261839960209 is an frugal number, since it uses more digits than its factorization.

261839960209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1023406 (or 511703 counting only the distinct ones).

The product of its (nonzero) digits is 2519424, while the sum is 55.

The spelling of 261839960209 in words is "two hundred sixty-one billion, eight hundred thirty-nine million, nine hundred sixty thousand, two hundred nine".