21816744 has 16 divisors (see below), whose sum is σ = 54541920. Its totient is φ = 7272240.

The previous prime is 21816733. The next prime is 21816749. The reversal of 21816744 is 44761812.

It is not an unprimeable number, because it can be changed into a prime (21816749) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 454492 + ... + 454539.

It is an arithmetic number, because the mean of its divisors is an integer number (3408870).

Almost surely, 2^21816744 is an apocalyptic number.

21816744 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21816744 is an abundant number, since it is smaller than the sum of its proper divisors (32725176).

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

21816744 is a wasteful number, since it uses less digits than its factorization.

21816744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 909040 (or 909036 counting only the distinct ones).

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

The square root of 21816744 is about 4670.8397531921. The cubic root of 21816744 is about 279.4237468302.

The spelling of 21816744 in words is "twenty-one million, eight hundred sixteen thousand, seven hundred forty-four".