19999840 has 72 divisors (see below), whose sum is σ = 54985392. Its totient is φ = 6854400.

The previous prime is 19999831. The next prime is 19999843. The reversal of 19999840 is 4899991.

It is a Harshad number since it is a multiple of its sum of digits (49).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19999843) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6565 + ... + 9115.

It is an arithmetic number, because the mean of its divisors is an integer number (763686).

Almost surely, 2^19999840 is an apocalyptic number.

19999840 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 19999840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27492696).

19999840 is an abundant number, since it is smaller than the sum of its proper divisors (34985552).

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

19999840 is a wasteful number, since it uses less digits than its factorization.

19999840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2580 (or 2565 counting only the distinct ones).

The product of its (nonzero) digits is 209952, while the sum is 49.

The square root of 19999840 is about 4472.1180664200. The cubic root of 19999840 is about 271.4410378129.

The spelling of 19999840 in words is "nineteen million, nine hundred ninety-nine thousand, eight hundred forty".