20505440 has 24 divisors (see below), whose sum is σ = 48444480. Its totient is φ = 8202112.

The previous prime is 20505431. The next prime is 20505449. The reversal of 20505440 is 4450502.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (20505431) and next prime (20505449).

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20505449) 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 3 ways as a sum of consecutive naturals, for example, 63920 + ... + 64239.

It is an arithmetic number, because the mean of its divisors is an integer number (2018520).

Almost surely, 2^20505440 is an apocalyptic number.

20505440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20505440 is an abundant number, since it is smaller than the sum of its proper divisors (27939040).

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

20505440 is a wasteful number, since it uses less digits than its factorization.

20505440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128174 (or 128166 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 20.

The square root of 20505440 is about 4528.2932767214. The cubic root of 20505440 is about 273.7093904996.

Adding to 20505440 its reverse (4450502), we get a palindrome (24955942).

The spelling of 20505440 in words is "twenty million, five hundred five thousand, four hundred forty".