21420343040021 has 2 divisors, whose sum is σ = 21420343040022. Its totient is φ = 21420343040020.

The previous prime is 21420343039999. The next prime is 21420343040081. The reversal of 21420343040021 is 12004034302412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14312307151921 + 7108035888100 = 3783161^2 + 2666090^2 .

It is a cyclic number.

It is not a de Polignac number, because 21420343040021 - 2²⁶ = 21420275931157 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21420343040081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10710171520010 + 10710171520011.

It is an arithmetic number, because the mean of its divisors is an integer number (10710171520011).

Almost surely, 2^{21420343040021} is an apocalyptic number.

It is an amenable number.

21420343040021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21420343040021 is an equidigital number, since it uses as much as digits as its factorization.

21420343040021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4608, while the sum is 26.

Adding to 21420343040021 its reverse (12004034302412), we get a palindrome (33424377342433).

The spelling of 21420343040021 in words is "twenty-one trillion, four hundred twenty billion, three hundred forty-three million, forty thousand, twenty-one".