21020020180021 has 2 divisors, whose sum is σ = 21020020180022. Its totient is φ = 21020020180020.

The previous prime is 21020020179979. The next prime is 21020020180051. The reversal of 21020020180021 is 12008102002012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13898647591921 + 7121372588100 = 3728089^2 + 2668590^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020020180021 - 2³⁹ = 20470264366133 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21020020180051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510010090010 + 10510010090011.

It is an arithmetic number, because the mean of its divisors is an integer number (10510010090011).

Almost surely, 2^{21020020180021} is an apocalyptic number.

It is an amenable number.

21020020180021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020020180021 is an equidigital number, since it uses as much as digits as its factorization.

21020020180021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 128, while the sum is 19.

Adding to 21020020180021 its reverse (12008102002012), we get a palindrome (33028122182033).

The spelling of 21020020180021 in words is "twenty-one trillion, twenty billion, twenty million, one hundred eighty thousand, twenty-one".