21672171 has 16 divisors (see below), whose sum is σ = 32178720. Its totient is φ = 14415840.

The previous prime is 21672151. The next prime is 21672181. The reversal of 21672171 is 17127612.

It is not a de Polignac number, because 21672171 - 2⁵ = 21672139 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21672151) 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 15 ways as a sum of consecutive naturals, for example, 22561 + ... + 23501.

It is an arithmetic number, because the mean of its divisors is an integer number (2011170).

Almost surely, 2^21672171 is an apocalyptic number.

21672171 is a deficient number, since it is larger than the sum of its proper divisors (10506549).

21672171 is an equidigital number, since it uses as much as digits as its factorization.

21672171 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1803 (or 1797 counting only the distinct ones).

The product of its digits is 1176, while the sum is 27.

The square root of 21672171 is about 4655.3379039550. The cubic root of 21672171 is about 278.8051593739.

Adding to 21672171 its reverse (17127612), we get a palindrome (38799783).

The spelling of 21672171 in words is "twenty-one million, six hundred seventy-two thousand, one hundred seventy-one".