20689909 has 2 divisors, whose sum is σ = 20689910. Its totient is φ = 20689908.

The previous prime is 20689891. The next prime is 20689913. The reversal of 20689909 is 90998602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14085009 + 6604900 = 3753^2 + 2570^2 .

It is a cyclic number.

It is not a de Polignac number, because 20689909 - 2¹⁵ = 20657141 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20689979) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10344954 + 10344955.

It is an arithmetic number, because the mean of its divisors is an integer number (10344955).

Almost surely, 2^20689909 is an apocalyptic number.

It is an amenable number.

20689909 is a deficient number, since it is larger than the sum of its proper divisors (1).

20689909 is an equidigital number, since it uses as much as digits as its factorization.

20689909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 69984, while the sum is 43.

The square root of 20689909 is about 4548.6161631863. The cubic root of 20689909 is about 274.5277138761.

The spelling of 20689909 in words is "twenty million, six hundred eighty-nine thousand, nine hundred nine".