18218781578321 has 2 divisors, whose sum is σ = 18218781578322. Its totient is φ = 18218781578320.

The previous prime is 18218781578281. The next prime is 18218781578359. The reversal of 18218781578321 is 12387518781281.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18036465388096 + 182316190225 = 4246936^2 + 426985^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18218781578321 is a prime.

It is not a weakly prime, because it can be changed into another prime (18218781578521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9109390789160 + 9109390789161.

It is an arithmetic number, because the mean of its divisors is an integer number (9109390789161).

Almost surely, 2^{18218781578321} is an apocalyptic number.

It is an amenable number.

18218781578321 is a deficient number, since it is larger than the sum of its proper divisors (1).

18218781578321 is an equidigital number, since it uses as much as digits as its factorization.

18218781578321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12042240, while the sum is 62.

The spelling of 18218781578321 in words is "eighteen trillion, two hundred eighteen billion, seven hundred eighty-one million, five hundred seventy-eight thousand, three hundred twenty-one".