20507909 has 2 divisors, whose sum is σ = 20507910. Its totient is φ = 20507908.

The previous prime is 20507891. The next prime is 20507911. The reversal of 20507909 is 90970502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12271009 + 8236900 = 3503^2 + 2870^2 .

It is a cyclic number.

It is not a de Polignac number, because 20507909 - 2⁸ = 20507653 is a prime.

Together with 20507911, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20507969) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10253954 + 10253955.

It is an arithmetic number, because the mean of its divisors is an integer number (10253955).

Almost surely, 2^20507909 is an apocalyptic number.

It is an amenable number.

20507909 is a deficient number, since it is larger than the sum of its proper divisors (1).

20507909 is an equidigital number, since it uses as much as digits as its factorization.

20507909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5670, while the sum is 32.

The square root of 20507909 is about 4528.5658877839. The cubic root of 20507909 is about 273.7203755742.

The spelling of 20507909 in words is "twenty million, five hundred seven thousand, nine hundred nine".