15999840 has 144 divisors (see below), whose sum is σ = 56137536. Its totient is φ = 4147200.

The previous prime is 15999833. The next prime is 15999853. The reversal of 15999840 is 4899951.

It is a tau number, because it is divible by the number of its divisors (144).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 58905 + ... + 59175.

It is an arithmetic number, because the mean of its divisors is an integer number (389844).

Almost surely, 2^15999840 is an apocalyptic number.

15999840 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 15999840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28068768).

15999840 is an abundant number, since it is smaller than the sum of its proper divisors (40137696).

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

15999840 is a wasteful number, since it uses less digits than its factorization.

15999840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 333 (or 322 counting only the distinct ones).

The product of its (nonzero) digits is 116640, while the sum is 45.

The square root of 15999840 is about 3999.9799999500. The cubic root of 15999840 is about 251.9833700288.

It can be divided in two parts, 159 and 99840, that added together give a palindrome (99999).

The spelling of 15999840 in words is "fifteen million, nine hundred ninety-nine thousand, eight hundred forty".