21004171 has 4 divisors (see below), whose sum is σ = 21013344. Its totient is φ = 20995000.

The previous prime is 21004169. The next prime is 21004183. The reversal of 21004171 is 17140012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21004171 - 2¹ = 21004169 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21004471) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2046 + ... + 6796.

It is an arithmetic number, because the mean of its divisors is an integer number (5253336).

Almost surely, 2^21004171 is an apocalyptic number.

21004171 is a deficient number, since it is larger than the sum of its proper divisors (9173).

21004171 is an equidigital number, since it uses as much as digits as its factorization.

21004171 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9172.

The product of its (nonzero) digits is 56, while the sum is 16.

The square root of 21004171 is about 4583.0307657706. The cubic root of 21004171 is about 275.9106822587.

Adding to 21004171 its reverse (17140012), we get a palindrome (38144183).

The spelling of 21004171 in words is "twenty-one million, four thousand, one hundred seventy-one".