218479640681 has 4 divisors (see below), whose sum is σ = 218863612500. Its totient is φ = 218095668864.

The previous prime is 218479640669. The next prime is 218479640693. The reversal of 218479640681 is 186046974812.

It is a happy number.

218479640681 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 is an interprime number because it is at equal distance from previous prime (218479640669) and next prime (218479640693).

It can be written as a sum of positive squares in 2 ways, for example, as 93305200681 + 125174440000 = 305459^2 + 353800^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-218479640681 is a prime.

It is a super-2 number, since 2×218479640681² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (218479640651) 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, 191985056 + ... + 191986193.

It is an arithmetic number, because the mean of its divisors is an integer number (54715903125).

Almost surely, 2^218479640681 is an apocalyptic number.

It is an amenable number.

218479640681 is a deficient number, since it is larger than the sum of its proper divisors (383971819).

218479640681 is an equidigital number, since it uses as much as digits as its factorization.

218479640681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 383971818.

The product of its (nonzero) digits is 4644864, while the sum is 56.

The spelling of 218479640681 in words is "two hundred eighteen billion, four hundred seventy-nine million, six hundred forty thousand, six hundred eighty-one".