• 520 is the only known number such that
the reverse of and the reverse of +1 have
the same set of prime factors. Here, the reversal of 520 and 521
are 25 = 5^{2} and 125 = 5^{3}, respectively.

• 520 can be written using four 4's:

520 has 16 divisors (see below), whose sum is σ = 1260. Its totient is φ = 192.

The previous prime is 509. The next prime is 521. The reversal of 520 is 25.

520 is nontrivially palindromic in base 14.

520 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

520 is an esthetic number in base 8, because in such base its adjacent digits differ by 1.

It can be written as a sum of positive squares in 2 ways, for example, as 484 + 36 = 22^2 + 6^2 .

It is a sliding number, since 520 = 20 + 500 and 1/20 + 1/500 = 0.0520.

520 is an idoneal number.

520 is an undulating number in base 5, base 8 and base 14.

It is a plaindrome in base 6 and base 15.

It is a nialpdrome in base 10, base 11 and base 13.

It is not an unprimeable number, because it can be changed into a prime (521) by changing a digit.

520 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (2) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 34 + ... + 46.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (630).

520 is an abundant number, since it is smaller than the sum of its proper divisors (740).

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

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

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

The sum of its prime factors is 24 (or 20 counting only the distinct ones).

The product of its (nonzero) digits is 10, while the sum is 7.

The square root of 520 is about 22.8035085020. The cubic root of 520 is about 8.0414515172.

Adding to 520 its reverse (25), we get a palindrome (545).

It can be divided in two parts, 5 and 20, that multiplied together give a square (100 = 10^{2}).

The spelling of 520 in words is "five hundred twenty", and thus it is an aban number and an oban number.

• e-mail: info -at- numbersaplenty.com • Privacy notice • done in 0.099 sec. • engine limits •