21671871 has 16 divisors (see below), whose sum is σ = 31844736. Its totient is φ = 13025376.

The previous prime is 21671869. The next prime is 21671879. The reversal of 21671871 is 17817612.

It is not a de Polignac number, because 21671871 - 2¹ = 21671869 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21671879) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4785 + ... + 8138.

It is an arithmetic number, because the mean of its divisors is an integer number (1990296).

Almost surely, 2^21671871 is an apocalyptic number.

21671871 is a deficient number, since it is larger than the sum of its proper divisors (10172865).

21671871 is a wasteful number, since it uses less digits than its factorization.

21671871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12982.

The product of its digits is 4704, while the sum is 33.

The square root of 21671871 is about 4655.3056827667. The cubic root of 21671871 is about 278.8038729018.

The spelling of 21671871 in words is "twenty-one million, six hundred seventy-one thousand, eight hundred seventy-one".