21866243 has 16 divisors (see below), whose sum is σ = 26040000. Its totient is φ = 17971200.

The previous prime is 21866239. The next prime is 21866249. The reversal of 21866243 is 34266812.

It is a cyclic number.

It is not a de Polignac number, because 21866243 - 2² = 21866239 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21866249) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16883 + ... + 18131.

It is an arithmetic number, because the mean of its divisors is an integer number (1627500).

Almost surely, 2^21866243 is an apocalyptic number.

21866243 is a deficient number, since it is larger than the sum of its proper divisors (4173757).

21866243 is a wasteful number, since it uses less digits than its factorization.

21866243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1358.

The product of its digits is 13824, while the sum is 32.

The square root of 21866243 is about 4676.1354770793. The cubic root of 21866243 is about 279.6349110762.

The spelling of 21866243 in words is "twenty-one million, eight hundred sixty-six thousand, two hundred forty-three".