21381423 has 16 divisors (see below), whose sum is σ = 33135360. Its totient is φ = 12010176.

The previous prime is 21381407. The next prime is 21381433. The reversal of 21381423 is 32418312.

It is not a de Polignac number, because 21381423 - 2⁴ = 21381407 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21381393 and 21381402.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21381433) 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 15 ways as a sum of consecutive naturals, for example, 7390 + ... + 9867.

It is an arithmetic number, because the mean of its divisors is an integer number (2070960).

Almost surely, 2^21381423 is an apocalyptic number.

21381423 is a deficient number, since it is larger than the sum of its proper divisors (11753937).

21381423 is a wasteful number, since it uses less digits than its factorization.

21381423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17326.

The product of its digits is 1152, while the sum is 24.

The square root of 21381423 is about 4624.0050821771. The cubic root of 21381423 is about 277.5527502999.

Adding to 21381423 its reverse (32418312), we get a palindrome (53799735).

The spelling of 21381423 in words is "twenty-one million, three hundred eighty-one thousand, four hundred twenty-three".