16637221 has 2 divisors, whose sum is σ = 16637222. Its totient is φ = 16637220.

The previous prime is 16637219. The next prime is 16637249. The reversal of 16637221 is 12273661.

It is an a-pointer prime, because the next prime (16637249) can be obtained adding 16637221 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15124321 + 1512900 = 3889^2 + 1230^2 .

It is a cyclic number.

It is not a de Polignac number, because 16637221 - 2¹ = 16637219 is a prime.

Together with 16637219, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 16637221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16637261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8318610 + 8318611.

It is an arithmetic number, because the mean of its divisors is an integer number (8318611).

Almost surely, 2^16637221 is an apocalyptic number.

It is an amenable number.

16637221 is a deficient number, since it is larger than the sum of its proper divisors (1).

16637221 is an equidigital number, since it uses as much as digits as its factorization.

16637221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3024, while the sum is 28.

The square root of 16637221 is about 4078.8749674389. The cubic root of 16637221 is about 255.2859588399.

The spelling of 16637221 in words is "sixteen million, six hundred thirty-seven thousand, two hundred twenty-one".