16440021 has 24 divisors (see below), whose sum is σ = 25727520. Its totient is φ = 10056096.

The previous prime is 16440019. The next prime is 16440029. The reversal of 16440021 is 12004461.

16440021 is a `hidden beast` number, since 1 + 644 + 0 + 0 + 21 = 666.

It is not a de Polignac number, because 16440021 - 2¹ = 16440019 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 16439976 and 16440003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16440029) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 26250 + ... + 26868.

It is an arithmetic number, because the mean of its divisors is an integer number (1071980).

Almost surely, 2^16440021 is an apocalyptic number.

It is an amenable number.

16440021 is a deficient number, since it is larger than the sum of its proper divisors (9287499).

16440021 is a wasteful number, since it uses less digits than its factorization.

16440021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 865 (or 862 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 16440021 is about 4054.6295761759. The cubic root of 16440021 is about 254.2733175042.

Adding to 16440021 its reverse (12004461), we get a palindrome (28444482).

The spelling of 16440021 in words is "sixteen million, four hundred forty thousand, twenty-one".