623821 has 4 divisors (see below), whose sum is σ = 680544. Its totient is φ = 567100.

The previous prime is 623803. The next prime is 623839. The reversal of 623821 is 128326.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (623803) and next prime (623839).

It is a cyclic number.

It is not a de Polignac number, because 623821 - 2¹⁵ = 591053 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 623792 and 623801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (623851) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28345 + ... + 28366.

It is an arithmetic number, because the mean of its divisors is an integer number (170136).

2⁶²³⁸²¹ is an apocalyptic number.

It is an amenable number.

623821 is a deficient number, since it is larger than the sum of its proper divisors (56723).

623821 is a wasteful number, since it uses less digits than its factorization.

623821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56722.

The product of its digits is 576, while the sum is 22.

The square root of 623821 is about 789.8233979821. The cubic root of 623821 is about 85.4450018493.

It can be divided in two parts, 623 and 821, that added together give a square (1444 = 38²).

The spelling of 623821 in words is "six hundred twenty-three thousand, eight hundred twenty-one".