16191221 has 4 divisors (see below), whose sum is σ = 16219392. Its totient is φ = 16163052.

The previous prime is 16191179. The next prime is 16191223. The reversal of 16191221 is 12219161.

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.

It is a cyclic number.

It is not a de Polignac number, because 16191221 - 2¹⁰ = 16190197 is a prime.

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 (16191223) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13205 + ... + 14378.

It is an arithmetic number, because the mean of its divisors is an integer number (4054848).

Almost surely, 2^16191221 is an apocalyptic number.

It is an amenable number.

16191221 is a deficient number, since it is larger than the sum of its proper divisors (28171).

16191221 is an equidigital number, since it uses as much as digits as its factorization.

16191221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28170.

The product of its digits is 216, while the sum is 23.

The square root of 16191221 is about 4023.8316316665. The cubic root of 16191221 is about 252.9840845701.

The spelling of 16191221 in words is "sixteen million, one hundred ninety-one thousand, two hundred twenty-one".