20520 has 64 divisors (see below), whose sum is σ = 72000. Its totient is φ = 5184.

The previous prime is 20509. The next prime is 20521. The reversal of 20520 is 2502.

20520 = T₅₉ + T₆₀ + ... + T₆₈.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a nialpdrome in base 12.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 20520.

It is not an unprimeable number, because it can be changed into a prime (20521) by changing a digit.

20520 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1071 + ... + 1089.

It is an arithmetic number, because the mean of its divisors is an integer number (1125).

2²⁰⁵²⁰ is an apocalyptic number.

20520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

20520 is the 72-nd decagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36000).

20520 is an abundant number, since it is smaller than the sum of its proper divisors (51480).

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

20520 is a wasteful number, since it uses less digits than its factorization.

20520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39 (or 29 counting only the distinct ones).

The product of its (nonzero) digits is 20, while the sum is 9.

The square root of 20520 is about 143.2480366358. The cubic root of 20520 is about 27.3774158123.

It can be divided in two parts, 205 and 20, that added together give a square (225 = 15²).

The spelling of 20520 in words is "twenty thousand, five hundred twenty".