663320021 has 32 divisors (see below), whose sum is σ = 839731200. Its totient is φ = 509955264.

The previous prime is 663320003. The next prime is 663320027. The reversal of 663320021 is 120023366.

It is a de Polignac number, because none of the positive numbers 2^k-663320021 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (663320027) 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 31 ways as a sum of consecutive naturals, for example, 1107080 + ... + 1107678.

It is an arithmetic number, because the mean of its divisors is an integer number (26241600).

Almost surely, 2^663320021 is an apocalyptic number.

It is an amenable number.

663320021 is a deficient number, since it is larger than the sum of its proper divisors (176411179).

663320021 is a wasteful number, since it uses less digits than its factorization.

663320021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 945.

The product of its (nonzero) digits is 1296, while the sum is 23.

The square root of 663320021 is about 25754.9999223452. Note that the first 4 decimals coincide. The cubic root of 663320021 is about 872.1162297199.

Adding to 663320021 its reverse (120023366), we get a palindrome (783343387).

The spelling of 663320021 in words is "six hundred sixty-three million, three hundred twenty thousand, twenty-one".