642840 has 64 divisors (see below), whose sum is σ = 2108160. Its totient is φ = 155520.

The previous prime is 642833. The next prime is 642853. The reversal of 642840 is 48246.

642840 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a nialpdrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 642840.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1077 + ... + 1563.

It is an arithmetic number, because the mean of its divisors is an integer number (32940).

2⁶⁴²⁸⁴⁰ is an apocalyptic number.

642840 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 642840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1054080).

642840 is an abundant number, since it is smaller than the sum of its proper divisors (1465320).

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

642840 is a wasteful number, since it uses less digits than its factorization.

642840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 512 (or 508 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 24.

The square root of 642840 is about 801.7730352163. The cubic root of 642840 is about 86.3046702335.

The spelling of 642840 in words is "six hundred forty-two thousand, eight hundred forty".