16651221 has 8 divisors (see below), whose sum is σ = 22801824. Its totient is φ = 10800720.

The previous prime is 16651199. The next prime is 16651237. The reversal of 16651221 is 12215661.

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

It is not a de Polignac number, because 16651221 - 2²¹ = 14554069 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 16651191 and 16651200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16651291) 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, 74895 + ... + 75116.

It is an arithmetic number, because the mean of its divisors is an integer number (2850228).

Almost surely, 2^16651221 is an apocalyptic number.

It is an amenable number.

16651221 is a deficient number, since it is larger than the sum of its proper divisors (6150603).

16651221 is a wasteful number, since it uses less digits than its factorization.

16651221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 150051.

The product of its digits is 720, while the sum is 24.

The square root of 16651221 is about 4080.5907660534. The cubic root of 16651221 is about 255.3575453426.

Adding to 16651221 its reverse (12215661), we get a palindrome (28866882).

The spelling of 16651221 in words is "sixteen million, six hundred fifty-one thousand, two hundred twenty-one".