21423871 has 16 divisors (see below), whose sum is σ = 25141248. Its totient is φ = 17877600.

The previous prime is 21423863. The next prime is 21423907. The reversal of 21423871 is 17832412.

It is a cyclic number.

It is not a de Polignac number, because 21423871 - 2³ = 21423863 is a prime.

It is a super-4 number, since 4×21423871⁴ (a number of 30 digits) contains 4444 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21423271) 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, 55746 + ... + 56128.

It is an arithmetic number, because the mean of its divisors is an integer number (1571328).

Almost surely, 2^21423871 is an apocalyptic number.

21423871 is a deficient number, since it is larger than the sum of its proper divisors (3717377).

21423871 is a wasteful number, since it uses less digits than its factorization.

21423871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 582.

The product of its digits is 2688, while the sum is 28.

The square root of 21423871 is about 4628.5927667057. The cubic root of 21423871 is about 277.7363017125.

The spelling of 21423871 in words is "twenty-one million, four hundred twenty-three thousand, eight hundred seventy-one".