19887021 has 24 divisors (see below), whose sum is σ = 35815104. Its totient is φ = 10330560.

The previous prime is 19887017. The next prime is 19887041. The reversal of 19887021 is 12078891.

It is not a de Polignac number, because 19887021 - 2² = 19887017 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19887041) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13656 + ... + 15041.

It is an arithmetic number, because the mean of its divisors is an integer number (1492296).

Almost surely, 2^19887021 is an apocalyptic number.

19887021 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

19887021 is a deficient number, since it is larger than the sum of its proper divisors (15928083).

19887021 is a wasteful number, since it uses less digits than its factorization.

19887021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28721 (or 28718 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 19887021 is about 4459.4866296470. The cubic root of 19887021 is about 270.9296758835.

It can be divided in two parts, 198870 and 21, that added together give a palindrome (198891).

The spelling of 19887021 in words is "nineteen million, eight hundred eighty-seven thousand, twenty-one".