21178423 has 8 divisors (see below), whose sum is σ = 25256448. Its totient is φ = 17363544.

The previous prime is 21178411. The next prime is 21178433. The reversal of 21178423 is 32487112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21178423 - 2¹³ = 21170231 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21178391 and 21178400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21178433) 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 7 ways as a sum of consecutive naturals, for example, 65611 + ... + 65932.

It is an arithmetic number, because the mean of its divisors is an integer number (3157056).

Almost surely, 2^21178423 is an apocalyptic number.

21178423 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21178423 is a deficient number, since it is larger than the sum of its proper divisors (4078025).

21178423 is a wasteful number, since it uses less digits than its factorization.

21178423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 131573.

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

The square root of 21178423 is about 4602.0020643194. The cubic root of 21178423 is about 276.6715731134.

The spelling of 21178423 in words is "twenty-one million, one hundred seventy-eight thousand, four hundred twenty-three".