820638 has 64 divisors (see below), whose sum is σ = 2257920. Its totient is φ = 215136.

The previous prime is 820637. The next prime is 820643. The reversal of 820638 is 836028.

820638 is a `hidden beast` number, since 8 + 20 + 638 = 666.

820638 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 (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (820637) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4831 + ... + 4997.

It is an arithmetic number, because the mean of its divisors is an integer number (35280).

2⁸²⁰⁶³⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 820638, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1128960).

820638 is an abundant number, since it is smaller than the sum of its proper divisors (1437282).

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

820638 is a wasteful number, since it uses less digits than its factorization.

820638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 198 (or 192 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

The square root of 820638 is about 905.8907218865. The cubic root of 820638 is about 93.6232848053.

The spelling of 820638 in words is "eight hundred twenty thousand, six hundred thirty-eight".