66604021 has 8 divisors (see below), whose sum is σ = 75818304. Its totient is φ = 57916320.

The previous prime is 66604019. The next prime is 66604037. The reversal of 66604021 is 12040666.

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 66604021 - 2¹ = 66604019 is a prime.

It is a super-2 number, since 2×66604021² = 8872191226736882, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66604001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 131376 + ... + 131881.

It is an arithmetic number, because the mean of its divisors is an integer number (9477288).

Almost surely, 2^66604021 is an apocalyptic number.

It is an amenable number.

66604021 is a deficient number, since it is larger than the sum of its proper divisors (9214283).

66604021 is a wasteful number, since it uses less digits than its factorization.

66604021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 263291.

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 66604021 is about 8161.1286596892. The cubic root of 66604021 is about 405.3530853687.

Adding to 66604021 its reverse (12040666), we get a palindrome (78644687).

The spelling of 66604021 in words is "sixty-six million, six hundred four thousand, twenty-one".