19813987 has 2 divisors, whose sum is σ = 19813988. Its totient is φ = 19813986.

The previous prime is 19813967. The next prime is 19814021. The reversal of 19813987 is 78931891.

It is a weak prime.

It is an emirp because it is prime and its reverse (78931891) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19813987 is a prime.

It is a super-3 number, since 3×19813987³ (a number of 23 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (19813957) 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, 9906993 + 9906994.

It is an arithmetic number, because the mean of its divisors is an integer number (9906994).

Almost surely, 2^19813987 is an apocalyptic number.

19813987 is a deficient number, since it is larger than the sum of its proper divisors (1).

19813987 is an equidigital number, since it uses as much as digits as its factorization.

19813987 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 108864, while the sum is 46.

The square root of 19813987 is about 4451.2904870386. The cubic root of 19813987 is about 270.5976109015.

The spelling of 19813987 in words is "nineteen million, eight hundred thirteen thousand, nine hundred eighty-seven".