21020011001921 has 2 divisors, whose sum is σ = 21020011001922. Its totient is φ = 21020011001920.

The previous prime is 21020011001771. The next prime is 21020011002059. The reversal of 21020011001921 is 12910011002012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20833245279025 + 186765722896 = 4564345^2 + 432164^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21020011001921 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21020011001893 and 21020011001902.

It is not a weakly prime, because it can be changed into another prime (21020011001621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510005500960 + 10510005500961.

It is an arithmetic number, because the mean of its divisors is an integer number (10510005500961).

Almost surely, 2^{21020011001921} is an apocalyptic number.

It is an amenable number.

21020011001921 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020011001921 is an equidigital number, since it uses as much as digits as its factorization.

21020011001921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72, while the sum is 20.

Adding to 21020011001921 its reverse (12910011002012), we get a palindrome (33930022003933).

The spelling of 21020011001921 in words is "twenty-one trillion, twenty billion, eleven million, one thousand, nine hundred twenty-one".