218681779379449 has 3 divisors (see below), whose sum is σ = 218681794167343. Its totient is φ = 218681764591556.

The previous prime is 218681779379447. The next prime is 218681779379471. The reversal of 218681779379449 is 944973977186812.

The square root of 218681779379449 is 14787893.

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 can be written as a sum of positive squares in only one way, i.e., 4272178955625 + 214409600423824 = 2066925^2 + 14642732^2 .

It is not a de Polignac number, because 218681779379449 - 2¹ = 218681779379447 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (218681779379447) 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, 7393947 + ... + 22181839.

Almost surely, 2^{218681779379449} is an apocalyptic number.

218681779379449 is the 14787893-rd square number.

218681779379449 is the 7393947-th centered octagonal number.

It is an amenable number.

218681779379449 is a deficient number, since it is larger than the sum of its proper divisors (14787894).

218681779379449 is an frugal number, since it uses more digits than its factorization.

218681779379449 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29575786 (or 14787893 counting only the distinct ones).

The product of its digits is 9217732608, while the sum is 85.

The spelling of 218681779379449 in words is "two hundred eighteen trillion, six hundred eighty-one billion, seven hundred seventy-nine million, three hundred seventy-nine thousand, four hundred forty-nine".