21423423 has 8 divisors (see below), whose sum is σ = 32645248. Its totient is φ = 12241944.

The previous prime is 21423421. The next prime is 21423487. The reversal of 21423423 is 32432412.

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

It is not a de Polignac number, because 21423423 - 2¹ = 21423421 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 1020163 = 21423423 / (2 + 1 + 4 + 2 + 3 + 4 + 2 + 3).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21423423.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21423421) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 510061 + ... + 510102.

It is an arithmetic number, because the mean of its divisors is an integer number (4080656).

Almost surely, 2^21423423 is an apocalyptic number.

21423423 is a deficient number, since it is larger than the sum of its proper divisors (11221825).

21423423 is a wasteful number, since it uses less digits than its factorization.

21423423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1020173.

The product of its digits is 1152, while the sum is 21.

The square root of 21423423 is about 4628.5443716140. The cubic root of 21423423 is about 277.7343657610.

Adding to 21423423 its reverse (32432412), we get a palindrome (53855835).

It can be divided in two parts, 2142 and 3423, that added together give a triangular number (5565 = T₁₀₅).

The spelling of 21423423 in words is "twenty-one million, four hundred twenty-three thousand, four hundred twenty-three".