20509171 has 2 divisors, whose sum is σ = 20509172. Its totient is φ = 20509170.

The previous prime is 20509147. The next prime is 20509183. The reversal of 20509171 is 17190502.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20509171 - 2¹⁹ = 19984883 is a prime.

It is not a weakly prime, because it can be changed into another prime (20509271) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10254585 + 10254586.

It is an arithmetic number, because the mean of its divisors is an integer number (10254586).

Almost surely, 2^20509171 is an apocalyptic number.

20509171 is a deficient number, since it is larger than the sum of its proper divisors (1).

20509171 is an equidigital number, since it uses as much as digits as its factorization.

20509171 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 630, while the sum is 25.

The square root of 20509171 is about 4528.7052233503. The cubic root of 20509171 is about 273.7259901240.

Adding to 20509171 its reverse (17190502), we get a palindrome (37699673).

The spelling of 20509171 in words is "twenty million, five hundred nine thousand, one hundred seventy-one".