21606243 has 8 divisors (see below), whose sum is σ = 28880400. Its totient is φ = 14368128.

The previous prime is 21606217. The next prime is 21606259. The reversal of 21606243 is 34260612.

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

It is not a de Polignac number, because 21606243 - 2¹⁴ = 21589859 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21606203) 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, 7578 + ... + 10031.

It is an arithmetic number, because the mean of its divisors is an integer number (3610050).

Almost surely, 2^21606243 is an apocalyptic number.

21606243 is a deficient number, since it is larger than the sum of its proper divisors (7274157).

21606243 is a wasteful number, since it uses less digits than its factorization.

21606243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18021.

The product of its (nonzero) digits is 1728, while the sum is 24.

The square root of 21606243 is about 4648.2516067872. The cubic root of 21606243 is about 278.5221583943.

Adding to 21606243 its reverse (34260612), we get a palindrome (55866855).

The spelling of 21606243 in words is "twenty-one million, six hundred six thousand, two hundred forty-three".