19986809 has 2 divisors, whose sum is σ = 19986810. Its totient is φ = 19986808.

The previous prime is 19986751. The next prime is 19986817. The reversal of 19986809 is 90868991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14417209 + 5569600 = 3797^2 + 2360^2 .

It is a cyclic number.

It is not a de Polignac number, because 19986809 - 2¹² = 19982713 is a prime.

It is not a weakly prime, because it can be changed into another prime (19980809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9993404 + 9993405.

It is an arithmetic number, because the mean of its divisors is an integer number (9993405).

Almost surely, 2^19986809 is an apocalyptic number.

It is an amenable number.

19986809 is a deficient number, since it is larger than the sum of its proper divisors (1).

19986809 is an equidigital number, since it uses as much as digits as its factorization.

19986809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 279936, while the sum is 50.

The square root of 19986809 is about 4470.6609131089. The cubic root of 19986809 is about 271.3820720635.

The spelling of 19986809 in words is "nineteen million, nine hundred eighty-six thousand, eight hundred nine".