4221821 has 4 divisors (see below), whose sum is σ = 4301532. Its totient is φ = 4142112.

The previous prime is 4221799. The next prime is 4221827. The reversal of 4221821 is 1281224.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3290596 + 931225 = 1814^2 + 965^2 .

It is a cyclic number.

It is not a de Polignac number, because 4221821 - 2¹⁴ = 4205437 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 4221793 and 4221802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (4221827) 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, 39776 + ... + 39881.

It is an arithmetic number, because the mean of its divisors is an integer number (1075383).

Almost surely, 2^4221821 is an apocalyptic number.

It is an amenable number.

4221821 is a deficient number, since it is larger than the sum of its proper divisors (79711).

4221821 is an equidigital number, since it uses as much as digits as its factorization.

4221821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79710.

The product of its digits is 256, while the sum is 20.

The square root of 4221821 is about 2054.7070350782. The cubic root of 4221821 is about 161.6217997623.

The spelling of 4221821 in words is "four million, two hundred twenty-one thousand, eight hundred twenty-one".