16428221 has 2 divisors, whose sum is σ = 16428222. Its totient is φ = 16428220.

The previous prime is 16428197. The next prime is 16428227. The reversal of 16428221 is 12282461.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13060996 + 3367225 = 3614^2 + 1835^2 .

It is a cyclic number.

It is not a de Polignac number, because 16428221 - 2⁶ = 16428157 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16428227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8214110 + 8214111.

It is an arithmetic number, because the mean of its divisors is an integer number (8214111).

Almost surely, 2^16428221 is an apocalyptic number.

It is an amenable number.

16428221 is a deficient number, since it is larger than the sum of its proper divisors (1).

16428221 is an equidigital number, since it uses as much as digits as its factorization.

16428221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1536, while the sum is 26.

The square root of 16428221 is about 4053.1741882135. The cubic root of 16428221 is about 254.2124671502.

Subtracting from 16428221 its reverse (12282461), we obtain a triangular number (4145760 = T₂₈₇₉).

The spelling of 16428221 in words is "sixteen million, four hundred twenty-eight thousand, two hundred twenty-one".