19815109 has 2 divisors, whose sum is σ = 19815110. Its totient is φ = 19815108.

The previous prime is 19815101. The next prime is 19815137. The reversal of 19815109 is 90151891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17556100 + 2259009 = 4190^2 + 1503^2 .

It is a cyclic number.

It is not a de Polignac number, because 19815109 - 2³ = 19815101 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19815101) 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, 9907554 + 9907555.

It is an arithmetic number, because the mean of its divisors is an integer number (9907555).

Almost surely, 2^19815109 is an apocalyptic number.

It is an amenable number.

19815109 is a deficient number, since it is larger than the sum of its proper divisors (1).

19815109 is an equidigital number, since it uses as much as digits as its factorization.

19815109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3240, while the sum is 34.

The square root of 19815109 is about 4451.4165161216. The cubic root of 19815109 is about 270.6027184851.

The spelling of 19815109 in words is "nineteen million, eight hundred fifteen thousand, one hundred nine".