21025656 has 80 divisors (see below), whose sum is σ = 59851440. Its totient is φ = 6894720.

The previous prime is 21025639. The next prime is 21025681. The reversal of 21025656 is 65652012.

21025656 is a `hidden beast` number, since 2 + 1 + 0 + 2 + 5 + 656 = 666.

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

It is a congruent number.

It is an unprimeable number.

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 19 ways as a sum of consecutive naturals, for example, 45780 + ... + 46236.

It is an arithmetic number, because the mean of its divisors is an integer number (748143).

Almost surely, 2^21025656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21025656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29925720).

21025656 is an abundant number, since it is smaller than the sum of its proper divisors (38825784).

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

21025656 is a wasteful number, since it uses less digits than its factorization.

21025656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 546 (or 533 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 21025656 is about 4585.3741395877. The cubic root of 21025656 is about 276.0047258170.

Adding to 21025656 its reverse (65652012), we get a palindrome (86677668).

The spelling of 21025656 in words is "twenty-one million, twenty-five thousand, six hundred fifty-six".