4390021 has 2 divisors, whose sum is σ = 4390022. Its totient is φ = 4390020.

The previous prime is 4389997. The next prime is 4390039. The reversal of 4390021 is 1200934.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3204100 + 1185921 = 1790^2 + 1089^2 .

It is a cyclic number.

It is not a de Polignac number, because 4390021 - 2⁵ = 4389989 is a prime.

It is equal to p₃₀₈₇₀₁ and since 4390021 and 308701 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (4390051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2195010 + 2195011.

It is an arithmetic number, because the mean of its divisors is an integer number (2195011).

Almost surely, 2^4390021 is an apocalyptic number.

It is an amenable number.

4390021 is a deficient number, since it is larger than the sum of its proper divisors (1).

4390021 is an equidigital number, since it uses as much as digits as its factorization.

4390021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 216, while the sum is 19.

The square root of 4390021 is about 2095.2376953463. The cubic root of 4390021 is about 163.7402814581.

Adding to 4390021 its reverse (1200934), we get a palindrome (5590955).

The spelling of 4390021 in words is "four million, three hundred ninety thousand, twenty-one".