18038628721 has 2 divisors, whose sum is σ = 18038628722. Its totient is φ = 18038628720.

The previous prime is 18038628683. The next prime is 18038628799. The reversal of 18038628721 is 12782683081.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9714073600 + 8324555121 = 98560^2 + 91239^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18038628721 is a prime.

It is a super-2 number, since 2×18038628721² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (18038628121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9019314360 + 9019314361.

It is an arithmetic number, because the mean of its divisors is an integer number (9019314361).

Almost surely, 2^18038628721 is an apocalyptic number.

It is an amenable number.

18038628721 is a deficient number, since it is larger than the sum of its proper divisors (1).

18038628721 is an equidigital number, since it uses as much as digits as its factorization.

18038628721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 258048, while the sum is 46.

The spelling of 18038628721 in words is "eighteen billion, thirty-eight million, six hundred twenty-eight thousand, seven hundred twenty-one".