9999840 has 96 divisors (see below), whose sum is σ = 32006016. Its totient is φ = 2624000.

The previous prime is 9999823. The next prime is 9999863. The reversal of 9999840 is 489999.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (96).

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

It is a nialpdrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 9999840.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 39715 + ... + 39965.

It is an arithmetic number, because the mean of its divisors is an integer number (333396).

Almost surely, 2^9999840 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 9999840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (16003008).

9999840 is an abundant number, since it is smaller than the sum of its proper divisors (22006176).

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

9999840 is a wasteful number, since it uses less digits than its factorization.

9999840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 352 (or 344 counting only the distinct ones).

The product of its (nonzero) digits is 209952, while the sum is 48.

The square root of 9999840 is about 3162.2523618459. The cubic root of 9999840 is about 215.4423199652.

The spelling of 9999840 in words is "nine million, nine hundred ninety-nine thousand, eight hundred forty".