6640421 has 8 divisors (see below), whose sum is σ = 7076160. Its totient is φ = 6209728.

The previous prime is 6640411. The next prime is 6640429. The reversal of 6640421 is 1240466.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 6640421 - 2¹⁸ = 6378277 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6640429) 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 in 7 ways as a sum of consecutive naturals, for example, 1670 + ... + 4008.

It is an arithmetic number, because the mean of its divisors is an integer number (884520).

Almost surely, 2^6640421 is an apocalyptic number.

It is an amenable number.

6640421 is a deficient number, since it is larger than the sum of its proper divisors (435739).

6640421 is a wasteful number, since it uses less digits than its factorization.

6640421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2523.

The product of its (nonzero) digits is 1152, while the sum is 23.

The square root of 6640421 is about 2576.9014338930. The cubic root of 6640421 is about 187.9598997768.

Adding to 6640421 its reverse (1240466), we get a palindrome (7880887).

The spelling of 6640421 in words is "six million, six hundred forty thousand, four hundred twenty-one".