21004165 has 48 divisors (see below), whose sum is σ = 32254848. Its totient is φ = 12849408.

The previous prime is 21004157. The next prime is 21004169. The reversal of 21004165 is 56140012.

It is not a de Polignac number, because 21004165 - 2³ = 21004157 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21004169) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 313462 + ... + 313528.

It is an arithmetic number, because the mean of its divisors is an integer number (671976).

Almost surely, 2^21004165 is an apocalyptic number.

It is an amenable number.

21004165 is a deficient number, since it is larger than the sum of its proper divisors (11250683).

21004165 is a wasteful number, since it uses less digits than its factorization.

21004165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 158 (or 145 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 21004165 is about 4583.0301111819. The cubic root of 21004165 is about 275.9106559867.

Adding to 21004165 its reverse (56140012), we get a palindrome (77144177).

The spelling of 21004165 in words is "twenty-one million, four thousand, one hundred sixty-five".