218387658581 has 2 divisors, whose sum is σ = 218387658582. Its totient is φ = 218387658580.

The previous prime is 218387658523. The next prime is 218387658583. The reversal of 218387658581 is 185856783812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 179496268900 + 38891389681 = 423670^2 + 197209^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-218387658581 is a prime.

It is a super-2 number, since 2×218387658581² (a number of 23 digits) contains 22 as substring.

Together with 218387658583, it forms a pair of twin primes.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (218387658583) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109193829290 + 109193829291.

It is an arithmetic number, because the mean of its divisors is an integer number (109193829291).

Almost surely, 2^218387658581 is an apocalyptic number.

It is an amenable number.

218387658581 is a deficient number, since it is larger than the sum of its proper divisors (1).

218387658581 is an equidigital number, since it uses as much as digits as its factorization.

218387658581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25804800, while the sum is 62.

The spelling of 218387658581 in words is "two hundred eighteen billion, three hundred eighty-seven million, six hundred fifty-eight thousand, five hundred eighty-one".