21152171 has 4 divisors (see below), whose sum is σ = 21420000. Its totient is φ = 20884344.

The previous prime is 21152143. The next prime is 21152207. The reversal of 21152171 is 17125112.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21152171 - 2¹⁰ = 21151147 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21151171) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 133796 + ... + 133953.

It is an arithmetic number, because the mean of its divisors is an integer number (5355000).

Almost surely, 2^21152171 is an apocalyptic number.

21152171 is a deficient number, since it is larger than the sum of its proper divisors (267829).

21152171 is an equidigital number, since it uses as much as digits as its factorization.

21152171 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 267828.

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

The square root of 21152171 is about 4599.1489430111. The cubic root of 21152171 is about 276.5572085191.

Adding to 21152171 its reverse (17125112), we get a palindrome (38277283).

The spelling of 21152171 in words is "twenty-one million, one hundred fifty-two thousand, one hundred seventy-one".