19987864 has 16 divisors (see below), whose sum is σ = 40360320. Its totient is φ = 9225120.

The previous prime is 19987861. The next prime is 19987879. The reversal of 19987864 is 46878991.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (52).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19987861) 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 in 3 ways as a sum of consecutive naturals, for example, 95992 + ... + 96199.

It is an arithmetic number, because the mean of its divisors is an integer number (2522520).

Almost surely, 2^19987864 is an apocalyptic number.

It is an amenable number.

19987864 is an abundant number, since it is smaller than the sum of its proper divisors (20372456).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

19987864 is a wasteful number, since it uses less digits than its factorization.

19987864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 192210 (or 192206 counting only the distinct ones).

The product of its digits is 870912, while the sum is 52.

The square root of 19987864 is about 4470.7789030548. The cubic root of 19987864 is about 271.3868469302.

The spelling of 19987864 in words is "nineteen million, nine hundred eighty-seven thousand, eight hundred sixty-four".