16557221 has 8 divisors (see below), whose sum is σ = 16868544. Its totient is φ = 16248960.

The previous prime is 16557199. The next prime is 16557223. The reversal of 16557221 is 12275561.

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 16557221 - 2⁶ = 16557157 is a prime.

It is a super-4 number, since 4×16557221⁴ (a number of 30 digits) contains 4444 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16557223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12056 + ... + 13358.

It is an arithmetic number, because the mean of its divisors is an integer number (2108568).

Almost surely, 2^16557221 is an apocalyptic number.

It is an amenable number.

16557221 is a deficient number, since it is larger than the sum of its proper divisors (311323).

16557221 is a wasteful number, since it uses less digits than its factorization.

16557221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1531.

The product of its digits is 4200, while the sum is 29.

The square root of 16557221 is about 4069.0565245521. The cubic root of 16557221 is about 254.8761207852.

The spelling of 16557221 in words is "sixteen million, five hundred fifty-seven thousand, two hundred twenty-one".