19957840 has 80 divisors (see below), whose sum is σ = 53603712. Its totient is φ = 6769152.

The previous prime is 19957811. The next prime is 19957841. The reversal of 19957840 is 4875991.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19957841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 87807 + ... + 88033.

Almost surely, 2^19957840 is an apocalyptic number.

19957840 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 19957840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26801856).

19957840 is an abundant number, since it is smaller than the sum of its proper divisors (33645872).

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

19957840 is a wasteful number, since it uses less digits than its factorization.

19957840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 404 (or 398 counting only the distinct ones).

The product of its (nonzero) digits is 90720, while the sum is 43.

The square root of 19957840 is about 4467.4198369976. The cubic root of 19957840 is about 271.2508944027.

The spelling of 19957840 in words is "nineteen million, nine hundred fifty-seven thousand, eight hundred forty".