21523423 has 16 divisors (see below), whose sum is σ = 23659200. Its totient is φ = 19551840.

The previous prime is 21523421. The next prime is 21523433. The reversal of 21523423 is 32432512.

It is not a de Polignac number, because 21523423 - 2¹ = 21523421 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21523394 and 21523403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523421) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 352813 + ... + 352873.

It is an arithmetic number, because the mean of its divisors is an integer number (1478700).

Almost surely, 2^21523423 is an apocalyptic number.

21523423 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21523423 is a deficient number, since it is larger than the sum of its proper divisors (2135777).

21523423 is an frugal number, since it uses more digits than its factorization.

21523423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 159 (or 113 counting only the distinct ones).

The product of its digits is 1440, while the sum is 22.

The square root of 21523423 is about 4639.3343272500. The cubic root of 21523423 is about 278.1658301879.

Adding to 21523423 its reverse (32432512), we get a palindrome (53955935).

The spelling of 21523423 in words is "twenty-one million, five hundred twenty-three thousand, four hundred twenty-three".