18389434751921 has 2 divisors, whose sum is σ = 18389434751922. Its totient is φ = 18389434751920.

The previous prime is 18389434751869. The next prime is 18389434752011. The reversal of 18389434751921 is 12915743498381.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14208489442225 + 4180945309696 = 3769415^2 + 2044736^2 .

It is a cyclic number.

It is not a de Polignac number, because 18389434751921 - 2¹⁴ = 18389434735537 is a prime.

It is not a weakly prime, because it can be changed into another prime (18389434751021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9194717375960 + 9194717375961.

It is an arithmetic number, because the mean of its divisors is an integer number (9194717375961).

Almost surely, 2^{18389434751921} is an apocalyptic number.

It is an amenable number.

18389434751921 is a deficient number, since it is larger than the sum of its proper divisors (1).

18389434751921 is an equidigital number, since it uses as much as digits as its factorization.

18389434751921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 52254720, while the sum is 65.

The spelling of 18389434751921 in words is "eighteen trillion, three hundred eighty-nine billion, four hundred thirty-four million, seven hundred fifty-one thousand, nine hundred twenty-one".