21864471 has 4 divisors (see below), whose sum is σ = 29152632. Its totient is φ = 14576312.

The previous prime is 21864457. The next prime is 21864509. The reversal of 21864471 is 17446812.

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 21864471 - 2⁶ = 21864407 is a prime.

It is a super-3 number, since 3×21864471³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21864571) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3644076 + ... + 3644081.

It is an arithmetic number, because the mean of its divisors is an integer number (7288158).

Almost surely, 2^21864471 is an apocalyptic number.

21864471 is a deficient number, since it is larger than the sum of its proper divisors (7288161).

21864471 is an equidigital number, since it uses as much as digits as its factorization.

21864471 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7288160.

The product of its digits is 10752, while the sum is 33.

The square root of 21864471 is about 4675.9460005436. The cubic root of 21864471 is about 279.6273571730.

The spelling of 21864471 in words is "twenty-one million, eight hundred sixty-four thousand, four hundred seventy-one".