16406221 has 4 divisors (see below), whose sum is σ = 17668252. Its totient is φ = 15144192.

The previous prime is 16406213. The next prime is 16406227. The reversal of 16406221 is 12260461.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2604996 + 13801225 = 1614^2 + 3715^2 .

It is a cyclic number.

It is not a de Polignac number, because 16406221 - 2³ = 16406213 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 16406192 and 16406201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16406227) 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, 630996 + ... + 631021.

It is an arithmetic number, because the mean of its divisors is an integer number (4417063).

Almost surely, 2^16406221 is an apocalyptic number.

It is an amenable number.

16406221 is a deficient number, since it is larger than the sum of its proper divisors (1262031).

16406221 is a wasteful number, since it uses less digits than its factorization.

16406221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1262030.

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 16406221 is about 4050.4593566656. The cubic root of 16406221 is about 254.0989394868.

Adding to 16406221 its reverse (12260461), we get a palindrome (28666682).

Subtracting from 16406221 its reverse (12260461), we obtain a triangular number (4145760 = T₂₈₇₉).

The spelling of 16406221 in words is "sixteen million, four hundred six thousand, two hundred twenty-one".