20420 has 12 divisors (see below), whose sum is σ = 42924. Its totient is φ = 8160.

The previous prime is 20411. The next prime is 20431. The reversal of 20420 is 2402.

It can be written as a sum of positive squares in 2 ways, for example, as 9604 + 10816 = 98^2 + 104^2 .

It is a nialpdrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 20398 and 20407.

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 20420.

It is an unprimeable number.

20420 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 3 ways as a sum of consecutive naturals, for example, 491 + ... + 530.

It is an arithmetic number, because the mean of its divisors is an integer number (3577).

2²⁰⁴²⁰ is an apocalyptic number.

20420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20420 is an abundant number, since it is smaller than the sum of its proper divisors (22504).

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 (21462).

20420 is a wasteful number, since it uses less digits than its factorization.

20420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1030 (or 1028 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 8.

The square root of 20420 is about 142.8985654232. The cubic root of 20420 is about 27.3328706379.

Adding to 20420 its reverse (2402), we get a palindrome (22822).

The spelling of 20420 in words is "twenty thousand, four hundred twenty", and thus it is an iban number.