16257221 has 2 divisors, whose sum is σ = 16257222. Its totient is φ = 16257220.

The previous prime is 16257209. The next prime is 16257223. The reversal of 16257221 is 12275261.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15880225 + 376996 = 3985^2 + 614^2 .

It is a cyclic number.

It is not a de Polignac number, because 16257221 - 2¹⁴ = 16240837 is a prime.

Together with 16257223, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16257223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8128610 + 8128611.

It is an arithmetic number, because the mean of its divisors is an integer number (8128611).

Almost surely, 2^16257221 is an apocalyptic number.

It is an amenable number.

16257221 is a deficient number, since it is larger than the sum of its proper divisors (1).

16257221 is an equidigital number, since it uses as much as digits as its factorization.

16257221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1680, while the sum is 26.

The square root of 16257221 is about 4032.0244294895. The cubic root of 16257221 is about 253.3273634712.

The spelling of 16257221 in words is "sixteen million, two hundred fifty-seven thousand, two hundred twenty-one".