16663451221 has 8 divisors (see below), whose sum is σ = 17841899160. Its totient is φ = 15507030528.

The previous prime is 16663451213. The next prime is 16663451261. The reversal of 16663451221 is 12215436661.

It can be written as a sum of positive squares in 4 ways, for example, as 1805060196 + 14858391025 = 42486^2 + 121895^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 16663451221 - 2³ = 16663451213 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16663451261) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5505246 + ... + 5508271.

It is an arithmetic number, because the mean of its divisors is an integer number (2230237395).

Almost surely, 2^16663451221 is an apocalyptic number.

It is an amenable number.

16663451221 is a deficient number, since it is larger than the sum of its proper divisors (1178447939).

16663451221 is a wasteful number, since it uses less digits than its factorization.

16663451221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11013623.

The product of its digits is 51840, while the sum is 37.

Adding to 16663451221 its reverse (12215436661), we get a palindrome (28878887882).

The spelling of 16663451221 in words is "sixteen billion, six hundred sixty-three million, four hundred fifty-one thousand, two hundred twenty-one".