21542423 has 4 divisors (see below), whose sum is σ = 24619920. Its totient is φ = 18464928.

The previous prime is 21542413. The next prime is 21542453. The reversal of 21542423 is 32424512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21542423 - 2⁸ = 21542167 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21542413) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1538738 + ... + 1538751.

It is an arithmetic number, because the mean of its divisors is an integer number (6154980).

Almost surely, 2^21542423 is an apocalyptic number.

21542423 is a deficient number, since it is larger than the sum of its proper divisors (3077497).

21542423 is an equidigital number, since it uses as much as digits as its factorization.

21542423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3077496.

The product of its digits is 1920, while the sum is 23.

The square root of 21542423 is about 4641.3815831065. The cubic root of 21542423 is about 278.2476572648.

Adding to 21542423 its reverse (32424512), we get a palindrome (53966935).

The spelling of 21542423 in words is "twenty-one million, five hundred forty-two thousand, four hundred twenty-three".