20405550 has 96 divisors (see below), whose sum is σ = 56246400. Its totient is φ = 4854400.

The previous prime is 20405549. The next prime is 20405551. The reversal of 20405550 is 5550402.

It is an interprime number because it is at equal distance from previous prime (20405549) and next prime (20405551).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20405551) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 136876 + ... + 137024.

It is an arithmetic number, because the mean of its divisors is an integer number (585900).

Almost surely, 2^20405550 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20405550, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28123200).

20405550 is an abundant number, since it is smaller than the sum of its proper divisors (35840850).

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

20405550 is a wasteful number, since it uses less digits than its factorization.

20405550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 258 (or 253 counting only the distinct ones).

The product of its (nonzero) digits is 1000, while the sum is 21.

The square root of 20405550 is about 4517.2502697991. The cubic root of 20405550 is about 273.2642184297.

Adding to 20405550 its reverse (5550402), we get a palindrome (25955952).

The spelling of 20405550 in words is "twenty million, four hundred five thousand, five hundred fifty".