21864756 has 12 divisors (see below), whose sum is σ = 51017792. Its totient is φ = 7288248.

The previous prime is 21864659. The next prime is 21864757. The reversal of 21864756 is 65746812.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21864757) 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, 911020 + ... + 911043.

Almost surely, 2^21864756 is an apocalyptic number.

It is an amenable number.

21864756 is an abundant number, since it is smaller than the sum of its proper divisors (29153036).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21864756 is a wasteful number, since it uses less digits than its factorization.

21864756 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1822070 (or 1822068 counting only the distinct ones).

The product of its digits is 80640, while the sum is 39.

The square root of 21864756 is about 4675.9764755610. The cubic root of 21864756 is about 279.6285721342.

The spelling of 21864756 in words is "twenty-one million, eight hundred sixty-four thousand, seven hundred fifty-six".