16720221 has 16 divisors (see below), whose sum is σ = 26000000. Its totient is φ = 9553824.

The previous prime is 16720217. The next prime is 16720243. The reversal of 16720221 is 12202761.

It is not a de Polignac number, because 16720221 - 2² = 16720217 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16720021) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7096 + ... + 9153.

It is an arithmetic number, because the mean of its divisors is an integer number (1625000).

Almost surely, 2^16720221 is an apocalyptic number.

It is an amenable number.

16720221 is a deficient number, since it is larger than the sum of its proper divisors (9279779).

16720221 is an equidigital number, since it uses as much as digits as its factorization.

16720221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16273 (or 16259 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 21.

The square root of 16720221 is about 4089.0366836212. The cubic root of 16720221 is about 255.7097795482.

Adding to 16720221 its reverse (12202761), we get a palindrome (28922982).

The spelling of 16720221 in words is "sixteen million, seven hundred twenty thousand, two hundred twenty-one".