19987281 has 24 divisors (see below), whose sum is σ = 30251520. Its totient is φ = 12700800.

The previous prime is 19987277. The next prime is 19987283. The reversal of 19987281 is 18278991.

It is not a de Polignac number, because 19987281 - 2² = 19987277 is a prime.

It is a super-2 number, since 2×19987281² = 798982803545922, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (19987283) 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 23 ways as a sum of consecutive naturals, for example, 19305 + ... + 20313.

It is an arithmetic number, because the mean of its divisors is an integer number (1260480).

Almost surely, 2^19987281 is an apocalyptic number.

It is an amenable number.

19987281 is a deficient number, since it is larger than the sum of its proper divisors (10264239).

19987281 is a wasteful number, since it uses less digits than its factorization.

19987281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1117 (or 1114 counting only the distinct ones).

The product of its digits is 72576, while the sum is 45.

The square root of 19987281 is about 4470.7137014128. The cubic root of 19987281 is about 271.3842083280.

The spelling of 19987281 in words is "nineteen million, nine hundred eighty-seven thousand, two hundred eighty-one".