19805609 has 2 divisors, whose sum is σ = 19805610. Its totient is φ = 19805608.

The previous prime is 19805603. The next prime is 19805633. The reversal of 19805609 is 90650891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18490000 + 1315609 = 4300^2 + 1147^2 .

It is a cyclic number.

It is not a de Polignac number, because 19805609 - 2¹² = 19801513 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (19805603) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9902804 + 9902805.

It is an arithmetic number, because the mean of its divisors is an integer number (9902805).

Almost surely, 2^19805609 is an apocalyptic number.

It is an amenable number.

19805609 is a deficient number, since it is larger than the sum of its proper divisors (1).

19805609 is an equidigital number, since it uses as much as digits as its factorization.

19805609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 19440, while the sum is 38.

The square root of 19805609 is about 4450.3493121327. The cubic root of 19805609 is about 270.5594663593.

The spelling of 19805609 in words is "nineteen million, eight hundred five thousand, six hundred nine".