21001108021 has 2 divisors, whose sum is σ = 21001108022. Its totient is φ = 21001108020.

The previous prime is 21001107989. The next prime is 21001108033. The reversal of 21001108021 is 12080110012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16748242225 + 4252865796 = 129415^2 + 65214^2 .

It is a cyclic number.

It is not a de Polignac number, because 21001108021 - 2⁵ = 21001107989 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21001107986 and 21001108004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21001109021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500554010 + 10500554011.

It is an arithmetic number, because the mean of its divisors is an integer number (10500554011).

Almost surely, 2^21001108021 is an apocalyptic number.

It is an amenable number.

21001108021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21001108021 is an equidigital number, since it uses as much as digits as its factorization.

21001108021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 32, while the sum is 16.

Adding to 21001108021 its reverse (12080110012), we get a palindrome (33081218033).

The spelling of 21001108021 in words is "twenty-one billion, one million, one hundred eight thousand, twenty-one".