840020 has 24 divisors (see below), whose sum is σ = 1786344. Its totient is φ = 331776.

The previous prime is 839999. The next prime is 840023. The reversal of 840020 is 20048.

It can be written as a sum of positive squares in 4 ways, for example, as 4624 + 835396 = 68^2 + 914^2 .

It is an Ulam number.

It is a junction number, because it is equal to n+sod(n) for n = 839977 and 840004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (840023) by changing a digit.

840020 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, 1724 + ... + 2156.

It is an arithmetic number, because the mean of its divisors is an integer number (74431).

2⁸⁴⁰⁰²⁰ is an apocalyptic number.

It is an amenable number.

840020 is an abundant number, since it is smaller than the sum of its proper divisors (946324).

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

840020 is a wasteful number, since it uses less digits than its factorization.

840020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 539 (or 537 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 840020 is about 916.5260498207. The cubic root of 840020 is about 94.3546284407.

Adding to 840020 its reverse (20048), we get a palindrome (860068).

The spelling of 840020 in words is "eight hundred forty thousand, twenty".