21420140171 has 2 divisors, whose sum is σ = 21420140172. Its totient is φ = 21420140170.

The previous prime is 21420140129. The next prime is 21420140173. The reversal of 21420140171 is 17104102412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21420140171 - 2³⁴ = 4240270987 is a prime.

Together with 21420140173, 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 (21420140173) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10710070085 + 10710070086.

It is an arithmetic number, because the mean of its divisors is an integer number (10710070086).

Almost surely, 2^21420140171 is an apocalyptic number.

21420140171 is a deficient number, since it is larger than the sum of its proper divisors (1).

21420140171 is an equidigital number, since it uses as much as digits as its factorization.

21420140171 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 448, while the sum is 23.

Adding to 21420140171 its reverse (17104102412), we get a palindrome (38524242583).

The spelling of 21420140171 in words is "twenty-one billion, four hundred twenty million, one hundred forty thousand, one hundred seventy-one".