19991440 has 80 divisors (see below), whose sum is σ = 54996480. Its totient is φ = 6612480.

The previous prime is 19991429. The next prime is 19991467. The reversal of 19991440 is 4419991.

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-3 number, since 3×19991440³ (a number of 23 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 19991440.

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, 15625 + ... + 16855.

It is an arithmetic number, because the mean of its divisors is an integer number (687456).

Almost surely, 2^19991440 is an apocalyptic number.

19991440 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 19991440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27498240).

19991440 is an abundant number, since it is smaller than the sum of its proper divisors (35005040).

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

19991440 is a wasteful number, since it uses less digits than its factorization.

19991440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1280 (or 1274 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 37.

The square root of 19991440 is about 4471.1788154803. The cubic root of 19991440 is about 271.4030304420.

The spelling of 19991440 in words is "nineteen million, nine hundred ninety-one thousand, four hundred forty".