19687813 has 2 divisors, whose sum is σ = 19687814. Its totient is φ = 19687812.

The previous prime is 19687807. The next prime is 19687847. The reversal of 19687813 is 31878691.

19687813 = 3137² + 3138².

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9847044 + 9840769 = 3138^2 + 3137^2 .

It is a cyclic number.

It is not a de Polignac number, because 19687813 - 2⁹ = 19687301 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19687813.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19687873) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9843906 + 9843907.

It is an arithmetic number, because the mean of its divisors is an integer number (9843907).

Almost surely, 2^19687813 is an apocalyptic number.

19687813 is the 3138-th centered square number.

It is an amenable number.

19687813 is a deficient number, since it is larger than the sum of its proper divisors (1).

19687813 is an equidigital number, since it uses as much as digits as its factorization.

19687813 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 72576, while the sum is 43.

The square root of 19687813 is about 4437.0951082888. The cubic root of 19687813 is about 270.0220055224.

The spelling of 19687813 in words is "nineteen million, six hundred eighty-seven thousand, eight hundred thirteen".