19780109 has 2 divisors, whose sum is σ = 19780110. Its totient is φ = 19780108.

The previous prime is 19780093. The next prime is 19780141. The reversal of 19780109 is 90108791.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16728100 + 3052009 = 4090^2 + 1747^2 .

It is a cyclic number.

It is not a de Polignac number, because 19780109 - 2⁴ = 19780093 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19780169) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9890054 + 9890055.

It is an arithmetic number, because the mean of its divisors is an integer number (9890055).

Almost surely, 2^19780109 is an apocalyptic number.

It is an amenable number.

19780109 is a deficient number, since it is larger than the sum of its proper divisors (1).

19780109 is an equidigital number, since it uses as much as digits as its factorization.

19780109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4536, while the sum is 35.

The square root of 19780109 is about 4447.4834457252. The cubic root of 19780109 is about 270.4433001177.

The spelling of 19780109 in words is "nineteen million, seven hundred eighty thousand, one hundred nine".