19989840 has 160 divisors (see below), whose sum is σ = 68745600. Its totient is φ = 4773888.

The previous prime is 19989839. The next prime is 19989859. The reversal of 19989840 is 4898991.

It is a Cunningham number, because it is equal to 4471²-1.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a self number, because there is not a number n which added to its sum of digits gives 19989840.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 134086 + ... + 134234.

It is an arithmetic number, because the mean of its divisors is an integer number (429660).

Almost surely, 2^19989840 is an apocalyptic number.

19989840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 19989840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34372800).

19989840 is an abundant number, since it is smaller than the sum of its proper divisors (48755760).

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

19989840 is a wasteful number, since it uses less digits than its factorization.

19989840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221 (or 215 counting only the distinct ones).

The product of its (nonzero) digits is 186624, while the sum is 48.

The square root of 19989840 is about 4470.9998881682. Note that the first 3 decimals coincide. The cubic root of 19989840 is about 271.3957897357.

The spelling of 19989840 in words is "nineteen million, nine hundred eighty-nine thousand, eight hundred forty".