19666399409 has 2 divisors, whose sum is σ = 19666399410. Its totient is φ = 19666399408.

The previous prime is 19666399373. The next prime is 19666399427. The reversal of 19666399409 is 90499366691.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16723662400 + 2942737009 = 129320^2 + 54247^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19666399409 is a prime.

It is not a weakly prime, because it can be changed into another prime (19666399469) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9833199704 + 9833199705.

It is an arithmetic number, because the mean of its divisors is an integer number (9833199705).

Almost surely, 2^19666399409 is an apocalyptic number.

It is an amenable number.

19666399409 is a deficient number, since it is larger than the sum of its proper divisors (1).

19666399409 is an equidigital number, since it uses as much as digits as its factorization.

19666399409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17006112, while the sum is 62.

The spelling of 19666399409 in words is "nineteen billion, six hundred sixty-six million, three hundred ninety-nine thousand, four hundred nine".