21543623 has 4 divisors (see below), whose sum is σ = 21686448. Its totient is φ = 21400800.

The previous prime is 21543619. The next prime is 21543653. The reversal of 21543623 is 32634512.

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 21543623 - 2² = 21543619 is a prime.

It is a super-2 number, since 2×21543623² = 928255383932258, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21543592 and 21543601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21543653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 71186 + ... + 71487.

It is an arithmetic number, because the mean of its divisors is an integer number (5421612).

Almost surely, 2^21543623 is an apocalyptic number.

21543623 is a deficient number, since it is larger than the sum of its proper divisors (142825).

21543623 is a wasteful number, since it uses less digits than its factorization.

21543623 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 142824.

The product of its digits is 4320, while the sum is 26.

The square root of 21543623 is about 4641.5108531598. The cubic root of 21543623 is about 278.2528236751.

The spelling of 21543623 in words is "twenty-one million, five hundred forty-three thousand, six hundred twenty-three".