19665440 has 48 divisors (see below), whose sum is σ = 47015640. Its totient is φ = 7772160.

The previous prime is 19665427. The next prime is 19665449. The reversal of 19665440 is 4456691.

It can be written as a sum of positive squares in 4 ways, for example, as 12418576 + 7246864 = 3524^2 + 2692^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 19665440.

It is not an unprimeable number, because it can be changed into a prime (19665449) 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 7 ways as a sum of consecutive naturals, for example, 13550 + ... + 14930.

Almost surely, 2^19665440 is an apocalyptic number.

19665440 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 19665440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23507820).

19665440 is an abundant number, since it is smaller than the sum of its proper divisors (27350200).

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

19665440 is a wasteful number, since it uses less digits than its factorization.

19665440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1485 (or 1477 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 35.

The square root of 19665440 is about 4434.5732601909. The cubic root of 19665440 is about 269.9196834724.

The spelling of 19665440 in words is "nineteen million, six hundred sixty-five thousand, four hundred forty".