21243623 has 8 divisors (see below), whose sum is σ = 21650928. Its totient is φ = 20839104.

The previous prime is 21243611. The next prime is 21243637. The reversal of 21243623 is 32634212.

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

It is a cyclic number.

It is not a de Polignac number, because 21243623 - 2²⁰ = 20195047 is a prime.

It is a super-2 number, since 2×21243623² = 902583036332258, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243683) 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, 20465 + ... + 21477.

It is an arithmetic number, because the mean of its divisors is an integer number (2706366).

Almost surely, 2^21243623 is an apocalyptic number.

21243623 is a deficient number, since it is larger than the sum of its proper divisors (407305).

21243623 is a wasteful number, since it uses less digits than its factorization.

21243623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1393.

The product of its digits is 1728, while the sum is 23.

The square root of 21243623 is about 4609.0804939814. The cubic root of 21243623 is about 276.9552030847.

Adding to 21243623 its reverse (32634212), we get a palindrome (53877835).

The spelling of 21243623 in words is "twenty-one million, two hundred forty-three thousand, six hundred twenty-three".