21584640 has 288 divisors, whose sum is σ = 87123456. Its totient is φ = 4423680.

The previous prime is 21584599. The next prime is 21584657. The reversal of 21584640 is 4648512.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21584598 and 21584607.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 295644 + ... + 295716.

It is an arithmetic number, because the mean of its divisors is an integer number (302512).

Almost surely, 2^21584640 is an apocalyptic number.

21584640 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 21584640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43561728).

21584640 is an abundant number, since it is smaller than the sum of its proper divisors (65538816).

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

21584640 is a wasteful number, since it uses less digits than its factorization.

21584640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115 (or 101 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 30.

The square root of 21584640 is about 4645.9272486771. The cubic root of 21584640 is about 278.4293006550.

The spelling of 21584640 in words is "twenty-one million, five hundred eighty-four thousand, six hundred forty".