19991985 has 16 divisors (see below), whose sum is σ = 34448064. Its totient is φ = 9842112.

The previous prime is 19991963. The next prime is 19991989. The reversal of 19991985 is 58919991.

It is not a de Polignac number, because 19991985 - 2¹⁴ = 19975601 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (19991989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 51067 + ... + 51456.

It is an arithmetic number, because the mean of its divisors is an integer number (2153004).

Almost surely, 2^19991985 is an apocalyptic number.

19991985 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

19991985 is a deficient number, since it is larger than the sum of its proper divisors (14456079).

19991985 is a wasteful number, since it uses less digits than its factorization.

19991985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102544.

The product of its digits is 262440, while the sum is 51.

The square root of 19991985 is about 4471.2397609612. The cubic root of 19991985 is about 271.4054967193.

The spelling of 19991985 in words is "nineteen million, nine hundred ninety-one thousand, nine hundred eighty-five".