20505280 has 56 divisors (see below), whose sum is σ = 49286160. Its totient is φ = 8125440.

The previous prime is 20505269. The next prime is 20505307. The reversal of 20505280 is 8250502.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44250 + ... + 44710.

It is an arithmetic number, because the mean of its divisors is an integer number (880110).

Almost surely, 2^20505280 is an apocalyptic number.

20505280 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 20505280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24643080).

20505280 is an abundant number, since it is smaller than the sum of its proper divisors (28780880).

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

20505280 is a wasteful number, since it uses less digits than its factorization.

20505280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 617 (or 607 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 22.

The square root of 20505280 is about 4528.2756099867. The cubic root of 20505280 is about 273.7086785972.

Adding to 20505280 its reverse (8250502), we get a palindrome (28755782).

The spelling of 20505280 in words is "twenty million, five hundred five thousand, two hundred eighty".