21020420191 has 2 divisors, whose sum is σ = 21020420192. Its totient is φ = 21020420190.

The previous prime is 21020420189. The next prime is 21020420203. The reversal of 21020420191 is 19102402012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21020420191 - 2¹ = 21020420189 is a prime.

Together with 21020420189, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21020420171) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510210095 + 10510210096.

It is an arithmetic number, because the mean of its divisors is an integer number (10510210096).

Almost surely, 2^21020420191 is an apocalyptic number.

21020420191 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020420191 is an equidigital number, since it uses as much as digits as its factorization.

21020420191 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 288, while the sum is 22.

The spelling of 21020420191 in words is "twenty-one billion, twenty million, four hundred twenty thousand, one hundred ninety-one".