19965840 has 80 divisors (see below), whose sum is σ = 64603008. Its totient is φ = 5091328.

The previous prime is 19965809. The next prime is 19965853. The reversal of 19965840 is 4856991.

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

It is a junction number, because it is equal to n+sod(n) for n = 19965792 and 19965801.

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, 3712 + ... + 7328.

Almost surely, 2^19965840 is an apocalyptic number.

19965840 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 19965840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32301504).

19965840 is an abundant number, since it is smaller than the sum of its proper divisors (44637168).

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

19965840 is a wasteful number, since it uses less digits than its factorization.

19965840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3656 (or 3650 counting only the distinct ones).

The product of its (nonzero) digits is 77760, while the sum is 42.

The square root of 19965840 is about 4468.3151186997. The cubic root of 19965840 is about 271.2871327477.

The spelling of 19965840 in words is "nineteen million, nine hundred sixty-five thousand, eight hundred forty".