21125171 has 4 divisors (see below), whose sum is σ = 21135912. Its totient is φ = 21114432.

The previous prime is 21125161. The next prime is 21125177. The reversal of 21125171 is 17152112.

It is a happy number.

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 21125171 - 2⁶ = 21125107 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21125177) 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, 1481 + ... + 6666.

It is an arithmetic number, because the mean of its divisors is an integer number (5283978).

Almost surely, 2^21125171 is an apocalyptic number.

21125171 is a deficient number, since it is larger than the sum of its proper divisors (10741).

21125171 is an equidigital number, since it uses as much as digits as its factorization.

21125171 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10740.

The product of its digits is 140, while the sum is 20.

The square root of 21125171 is about 4596.2126800225. The cubic root of 21125171 is about 276.4394865758.

Adding to 21125171 its reverse (17152112), we get a palindrome (38277283).

The spelling of 21125171 in words is "twenty-one million, one hundred twenty-five thousand, one hundred seventy-one".