16777221 has 4 divisors (see below), whose sum is σ = 22369632. Its totient is φ = 11184812.

The previous prime is 16777213. The next prime is 16777259. The reversal of 16777221 is 12277761.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12277761 = 3 ⋅4092587.

It is a cyclic number.

It is not a de Polignac number, because 16777221 - 2³ = 16777213 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16777291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (3) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2796201 + ... + 2796206.

It is an arithmetic number, because the mean of its divisors is an integer number (5592408).

Almost surely, 2^16777221 is an apocalyptic number.

It is an amenable number.

16777221 is a deficient number, since it is larger than the sum of its proper divisors (5592411).

16777221 is an equidigital number, since it uses as much as digits as its factorization.

16777221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5592410.

The product of its digits is 8232, while the sum is 33.

The square root of 16777221 is about 4096.0006103515. Note that the first 3 decimals coincide. The cubic root of 16777221 is about 256.0000254313. Note that the first 4 decimals are identical.

The spelling of 16777221 in words is "sixteen million, seven hundred seventy-seven thousand, two hundred twenty-one".