420840 has 96 divisors (see below), whose sum is σ = 1572480. Its totient is φ = 95616.

The previous prime is 420811. The next prime is 420851. The reversal of 420840 is 48024.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an Ulam number.

It is an unprimeable number.

420840 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 (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2437 + ... + 2603.

It is an arithmetic number, because the mean of its divisors is an integer number (16380).

2⁴²⁰⁸⁴⁰ is an apocalyptic number.

420840 is a gapful number since it is divisible by the number (40) 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 420840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (786240).

420840 is an abundant number, since it is smaller than the sum of its proper divisors (1151640).

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

420840 is a wasteful number, since it uses less digits than its factorization.

420840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 191 (or 184 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 18.

The square root of 420840 is about 648.7218201972. The cubic root of 420840 is about 74.9386164412.

Adding to 420840 its reverse (48024), we get a palindrome (468864).

Subtracting from 420840 its reverse (48024), we obtain a triangular number (372816 = T₈₆₃).

The spelling of 420840 in words is "four hundred twenty thousand, eight hundred forty".