21572423 has 4 divisors (see below), whose sum is σ = 21781968. Its totient is φ = 21362880.

The previous prime is 21572417. The next prime is 21572477. The reversal of 21572423 is 32427512.

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 21572423 - 2⁴ = 21572407 is a prime.

It is a super-4 number, since 4×21572423⁴ (a number of 30 digits) contains 4444 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21572392 and 21572401.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21572623) 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, 104618 + ... + 104823.

It is an arithmetic number, because the mean of its divisors is an integer number (5445492).

Almost surely, 2^21572423 is an apocalyptic number.

21572423 is a deficient number, since it is larger than the sum of its proper divisors (209545).

21572423 is a wasteful number, since it uses less digits than its factorization.

21572423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 209544.

The product of its digits is 3360, while the sum is 26.

The square root of 21572423 is about 4644.6122550758. The cubic root of 21572423 is about 278.3767600098.

Adding to 21572423 its reverse (32427512), we get a palindrome (53999935).

The spelling of 21572423 in words is "twenty-one million, five hundred seventy-two thousand, four hundred twenty-three".