21864549 has 8 divisors (see below), whose sum is σ = 33317440. Its totient is φ = 12494016.

The previous prime is 21864547. The next prime is 21864553. The reversal of 21864549 is 94546812.

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

It is not a de Polignac number, because 21864549 - 2¹ = 21864547 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21864547) 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 7 ways as a sum of consecutive naturals, for example, 520564 + ... + 520605.

It is an arithmetic number, because the mean of its divisors is an integer number (4164680).

Almost surely, 2^21864549 is an apocalyptic number.

It is an amenable number.

21864549 is a deficient number, since it is larger than the sum of its proper divisors (11452891).

21864549 is a wasteful number, since it uses less digits than its factorization.

21864549 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1041179.

The product of its digits is 69120, while the sum is 39.

The square root of 21864549 is about 4675.9543410944. The cubic root of 21864549 is about 279.6276896898.

The spelling of 21864549 in words is "twenty-one million, eight hundred sixty-four thousand, five hundred forty-nine".