21051023921 has 2 divisors, whose sum is σ = 21051023922. Its totient is φ = 21051023920.

The previous prime is 21051023893. The next prime is 21051023923. The reversal of 21051023921 is 12932015012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20089093696 + 961930225 = 141736^2 + 31015^2 .

It is a cyclic number.

It is not a de Polignac number, because 21051023921 - 2¹⁰ = 21051022897 is a prime.

Together with 21051023923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21051023923) 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, 10525511960 + 10525511961.

It is an arithmetic number, because the mean of its divisors is an integer number (10525511961).

Almost surely, 2^21051023921 is an apocalyptic number.

It is an amenable number.

21051023921 is a deficient number, since it is larger than the sum of its proper divisors (1).

21051023921 is an equidigital number, since it uses as much as digits as its factorization.

21051023921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1080, while the sum is 26.

Adding to 21051023921 its reverse (12932015012), we get a palindrome (33983038933).

The spelling of 21051023921 in words is "twenty-one billion, fifty-one million, twenty-three thousand, nine hundred twenty-one".