21030656 has 36 divisors (see below), whose sum is σ = 42408912. Its totient is φ = 10407936.

The previous prime is 21030637. The next prime is 21030677. The reversal of 21030656 is 65603012.

It is a hoax number, since the sum of its digits (23) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28565 + ... + 29291.

Almost surely, 2^21030656 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 21030656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21204456).

21030656 is an abundant number, since it is smaller than the sum of its proper divisors (21378256).

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

21030656 is an equidigital number, since it uses as much as digits as its factorization.

21030656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 856 (or 842 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 23.

The square root of 21030656 is about 4585.9193189588. The cubic root of 21030656 is about 276.0266024908.

Adding to 21030656 its reverse (65603012), we get a palindrome (86633668).

The spelling of 21030656 in words is "twenty-one million, thirty thousand, six hundred fifty-six".