20808440 has 64 divisors (see below), whose sum is σ = 49109760. Its totient is φ = 7925760.

The previous prime is 20808421. The next prime is 20808449. The reversal of 20808440 is 4480802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20808449) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 120194 + ... + 120366.

It is an arithmetic number, because the mean of its divisors is an integer number (767340).

Almost surely, 2^20808440 is an apocalyptic number.

20808440 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 20808440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24554880).

20808440 is an abundant number, since it is smaller than the sum of its proper divisors (28301320).

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

20808440 is a wasteful number, since it uses less digits than its factorization.

20808440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 312 (or 308 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 26.

The square root of 20808440 is about 4561.6269027618. The cubic root of 20808440 is about 275.0509657605.

The spelling of 20808440 in words is "twenty million, eight hundred eight thousand, four hundred forty".