43821 has 10 divisors (see below), whose sum is σ = 65582. Its totient is φ = 29160.

The previous prime is 43801. The next prime is 43853. The reversal of 43821 is 12834.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 35721 + 8100 = 189^2 + 90^2 .

It is not a de Polignac number, because 43821 - 2⁵ = 43789 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a nialpdrome in base 9.

It is a junction number, because it is equal to n+sod(n) for n = 43794 and 43803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (43801) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 190 + ... + 351.

2⁴³⁸²¹ is an apocalyptic number.

It is an amenable number.

43821 is a deficient number, since it is larger than the sum of its proper divisors (21761).

43821 is an equidigital number, since it uses as much as digits as its factorization.

43821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 553 (or 544 counting only the distinct ones).

The product of its digits is 192, while the sum is 18.

The square root of 43821 is about 209.3346602930. The cubic root of 43821 is about 35.2555446235.

The spelling of 43821 in words is "forty-three thousand, eight hundred twenty-one".