16616221 has 2 divisors, whose sum is σ = 16616222. Its totient is φ = 16616220.

The previous prime is 16616213. The next prime is 16616251. The reversal of 16616221 is 12261661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12040900 + 4575321 = 3470^2 + 2139^2 .

It is a cyclic number.

It is not a de Polignac number, because 16616221 - 2³ = 16616213 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16616251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8308110 + 8308111.

It is an arithmetic number, because the mean of its divisors is an integer number (8308111).

Almost surely, 2^16616221 is an apocalyptic number.

It is an amenable number.

16616221 is a deficient number, since it is larger than the sum of its proper divisors (1).

16616221 is an equidigital number, since it uses as much as digits as its factorization.

16616221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 864, while the sum is 25.

The square root of 16616221 is about 4076.2999153644. The cubic root of 16616221 is about 255.1785037481.

Adding to 16616221 its reverse (12261661), we get a palindrome (28877882).

The spelling of 16616221 in words is "sixteen million, six hundred sixteen thousand, two hundred twenty-one".