16644421 has 4 divisors (see below), whose sum is σ = 16657344. Its totient is φ = 16631500.

The previous prime is 16644403. The next prime is 16644443. The reversal of 16644421 is 12444661.

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 16644421 - 2¹⁷ = 16513349 is a prime.

It is a super-3 number, since 3×16644421³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 16644421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16641421) 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, 4285 + ... + 7186.

It is an arithmetic number, because the mean of its divisors is an integer number (4164336).

Almost surely, 2^16644421 is an apocalyptic number.

It is an amenable number.

16644421 is a deficient number, since it is larger than the sum of its proper divisors (12923).

16644421 is a wasteful number, since it uses less digits than its factorization.

16644421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12922.

The product of its digits is 4608, while the sum is 28.

The square root of 16644421 is about 4079.7574682817. The cubic root of 16644421 is about 255.3227797692.

The spelling of 16644421 in words is "sixteen million, six hundred forty-four thousand, four hundred twenty-one".