20820 has 24 divisors (see below), whose sum is σ = 58464. Its totient is φ = 5536.

The previous prime is 20809. The next prime is 20849. The reversal of 20820 is 2802.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 20796 and 20805.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 20820.

It is an unprimeable number.

20820 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 7 ways as a sum of consecutive naturals, for example, 114 + ... + 233.

It is an arithmetic number, because the mean of its divisors is an integer number (2436).

2²⁰⁸²⁰ is an apocalyptic number.

20820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20820 is an abundant number, since it is smaller than the sum of its proper divisors (37644).

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29232).

20820 is a wasteful number, since it uses less digits than its factorization.

20820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 359 (or 357 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 12.

The square root of 20820 is about 144.2913718834. The cubic root of 20820 is about 27.5101890618.

The spelling of 20820 in words is "twenty thousand, eight hundred twenty".