15985440 has 144 divisors (see below), whose sum is σ = 57847608. Its totient is φ = 4005888.

The previous prime is 15985433. The next prime is 15985447. The reversal of 15985440 is 4458951.

It is an interprime number because it is at equal distance from previous prime (15985433) and next prime (15985447).

It can be written as a sum of positive squares in 4 ways, for example, as 12873744 + 3111696 = 3588^2 + 1764^2 .

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 (36).

It is a junction number, because it is equal to n+sod(n) for n = 15985395 and 15985404.

It is not an unprimeable number, because it can be changed into a prime (15985447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 24154 + ... + 24806.

Almost surely, 2^15985440 is an apocalyptic number.

15985440 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 15985440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28923804).

15985440 is an abundant number, since it is smaller than the sum of its proper divisors (41862168).

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

15985440 is a wasteful number, since it uses less digits than its factorization.

15985440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 691 (or 680 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 36.

The square root of 15985440 is about 3998.1795857615. The cubic root of 15985440 is about 251.9077515715.

The spelling of 15985440 in words is "fifteen million, nine hundred eighty-five thousand, four hundred forty".