20018381921 has 2 divisors, whose sum is σ = 20018381922. Its totient is φ = 20018381920.

The previous prime is 20018381863. The next prime is 20018381939. The reversal of 20018381921 is 12918381002.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19927274896 + 91107025 = 141164^2 + 9545^2 .

It is a cyclic number.

It is not a de Polignac number, because 20018381921 - 2¹⁸ = 20018119777 is a prime.

It is a super-2 number, since 2×20018381921² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20018381951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10009190960 + 10009190961.

It is an arithmetic number, because the mean of its divisors is an integer number (10009190961).

Almost surely, 2^20018381921 is an apocalyptic number.

It is an amenable number.

20018381921 is a deficient number, since it is larger than the sum of its proper divisors (1).

20018381921 is an equidigital number, since it uses as much as digits as its factorization.

20018381921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6912, while the sum is 35.

The spelling of 20018381921 in words is "twenty billion, eighteen million, three hundred eighty-one thousand, nine hundred twenty-one".