19998987 has 16 divisors (see below), whose sum is σ = 28357632. Its totient is φ = 12493440.

The previous prime is 19998977. The next prime is 19998989. The reversal of 19998987 is 78989991.

It is not a de Polignac number, because 19998987 - 2⁷ = 19998859 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 19998987.

It is not an unprimeable number, because it can be changed into a prime (19998989) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13098 + ... + 14544.

It is an arithmetic number, because the mean of its divisors is an integer number (1772352).

Almost surely, 2^19998987 is an apocalyptic number.

19998987 is a gapful number since it is divisible by the number (17) formed by its first and last digit.

19998987 is a deficient number, since it is larger than the sum of its proper divisors (8358645).

19998987 is a wasteful number, since it uses less digits than its factorization.

19998987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1738.

The product of its digits is 2939328, while the sum is 60.

The square root of 19998987 is about 4472.0226967224. The cubic root of 19998987 is about 271.4371787404.

The spelling of 19998987 in words is "nineteen million, nine hundred ninety-eight thousand, nine hundred eighty-seven".