21824640 has 160 divisors (see below), whose sum is σ = 78124860. Its totient is φ = 5806080.

The previous prime is 21824629. The next prime is 21824657. The reversal of 21824640 is 4642812.

21824640 is a `hidden beast` number, since 2 + 18 + 2 + 4 + 640 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 18045504 + 3779136 = 4248^2 + 1944^2 .

It is a tau number, because it is divible by the number of its divisors (160).

It is a super-2 number, since 2×21824640² = 952629822259200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 51630 + ... + 52050.

Almost surely, 2^21824640 is an apocalyptic number.

21824640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21824640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39062430).

21824640 is an abundant number, since it is smaller than the sum of its proper divisors (56300220).

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

21824640 is an equidigital number, since it uses as much as digits as its factorization.

21824640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 452 (or 431 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 27.

The square root of 21824640 is about 4671.6849208824. The cubic root of 21824640 is about 279.4574528037.

The spelling of 21824640 in words is "twenty-one million, eight hundred twenty-four thousand, six hundred forty".