20665440 has 144 divisors (see below), whose sum is σ = 71705088. Its totient is φ = 5419008.

The previous prime is 20665433. The next prime is 20665441. The reversal of 20665440 is 4456602.

It is a happy number.

20665440 is a `hidden beast` number, since 2 + 0 + 6 + 654 + 4 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20665441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 162657 + ... + 162783.

It is an arithmetic number, because the mean of its divisors is an integer number (497952).

Almost surely, 2^20665440 is an apocalyptic number.

20665440 is a gapful number since it is divisible by the number (20) 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 20665440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35852544).

20665440 is an abundant number, since it is smaller than the sum of its proper divisors (51039648).

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

20665440 is a wasteful number, since it uses less digits than its factorization.

20665440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 261 (or 250 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 27.

The square root of 20665440 is about 4545.9256483141. The cubic root of 20665440 is about 274.4194474341.

The spelling of 20665440 in words is "twenty million, six hundred sixty-five thousand, four hundred forty".