6420 has 24 divisors (see below), whose sum is σ = 18144. Its totient is φ = 1696.

The previous prime is 6397. The next prime is 6421. The reversal of 6420 is 246.

6420 = T₃₆ + T₃₇ + ... + T₄₃.

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

It is an Ulam number.

It is a straight-line number, since its digits are in arithmetic progression.

It is a nialpdrome in base 10.

It is a junction number, because it is equal to n+sod(n) for n = 6396 and 6405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6421) by changing a digit.

6420 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 (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7 + ... + 113.

It is an arithmetic number, because the mean of its divisors is an integer number (756).

2⁶⁴²⁰ is an apocalyptic number.

6420 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 6420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (9072).

6420 is an abundant number, since it is smaller than the sum of its proper divisors (11724).

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

6420 is a wasteful number, since it uses less digits than its factorization.

6420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119 (or 117 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 12.

The square root of 6420 is about 80.1249024960. The cubic root of 6420 is about 18.5856751770.

6420 divided by its sum of digits (12) gives a palindrome (535).

Adding to 6420 its reverse (246), we get a palindrome (6666).

The spelling of 6420 in words is "six thousand, four hundred twenty".