19790809 has 2 divisors, whose sum is σ = 19790810. Its totient is φ = 19790808.

The previous prime is 19790801. The next prime is 19790831. The reversal of 19790809 is 90809791.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16000000 + 3790809 = 4000^2 + 1947^2 .

It is a cyclic number.

It is not a de Polignac number, because 19790809 - 2³ = 19790801 is a prime.

It is a super-2 number, since 2×19790809² = 783352241748962, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (19790801) 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, 9895404 + 9895405.

It is an arithmetic number, because the mean of its divisors is an integer number (9895405).

Almost surely, 2^19790809 is an apocalyptic number.

It is an amenable number.

19790809 is a deficient number, since it is larger than the sum of its proper divisors (1).

19790809 is an equidigital number, since it uses as much as digits as its factorization.

19790809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 40824, while the sum is 43.

The square root of 19790809 is about 4448.6862105570. The cubic root of 19790809 is about 270.4920565339.

The spelling of 19790809 in words is "nineteen million, seven hundred ninety thousand, eight hundred nine".