51505220 has 24 divisors (see below), whose sum is σ = 116481624. Its totient is φ = 19017216.

The previous prime is 51505213. The next prime is 51505273. The reversal of 51505220 is 2250515.

It can be written as a sum of positive squares in 4 ways, for example, as 9721924 + 41783296 = 3118^2 + 6464^2 .

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

It is a junction number, because it is equal to n+sod(n) for n = 51505192 and 51505201.

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, 98789 + ... + 99308.

It is an arithmetic number, because the mean of its divisors is an integer number (4853401).

Almost surely, 2^51505220 is an apocalyptic number.

It is an amenable number.

51505220 is an abundant number, since it is smaller than the sum of its proper divisors (64976404).

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

51505220 is a wasteful number, since it uses less digits than its factorization.

51505220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 198119 (or 198117 counting only the distinct ones).

The product of its (nonzero) digits is 500, while the sum is 20.

The square root of 51505220 is about 7176.7137326216. The cubic root of 51505220 is about 372.0635128770.

Adding to 51505220 its reverse (2250515), we get a palindrome (53755735).

The spelling of 51505220 in words is "fifty-one million, five hundred five thousand, two hundred twenty".