18038221921 has 2 divisors, whose sum is σ = 18038221922. Its totient is φ = 18038221920.

The previous prime is 18038221867. The next prime is 18038221933. The reversal of 18038221921 is 12912283081.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9194700321 + 8843521600 = 95889^2 + 94040^2 .

It is a cyclic number.

It is not a de Polignac number, because 18038221921 - 2¹³ = 18038213729 is a prime.

It is not a weakly prime, because it can be changed into another prime (18038231921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9019110960 + 9019110961.

It is an arithmetic number, because the mean of its divisors is an integer number (9019110961).

Almost surely, 2^18038221921 is an apocalyptic number.

It is an amenable number.

18038221921 is a deficient number, since it is larger than the sum of its proper divisors (1).

18038221921 is an equidigital number, since it uses as much as digits as its factorization.

18038221921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13824, while the sum is 37.

The spelling of 18038221921 in words is "eighteen billion, thirty-eight million, two hundred twenty-one thousand, nine hundred twenty-one".