21530656 has 48 divisors (see below), whose sum is σ = 48758976. Its totient is φ = 9167616.

The previous prime is 21530627. The next prime is 21530669. The reversal of 21530656 is 65603512.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 61875 + ... + 62221.

It is an arithmetic number, because the mean of its divisors is an integer number (1015812).

Almost surely, 2^21530656 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 21530656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24379488).

21530656 is an abundant number, since it is smaller than the sum of its proper divisors (27228320).

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

21530656 is a wasteful number, since it uses less digits than its factorization.

21530656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 641 (or 633 counting only the distinct ones).

The product of its (nonzero) digits is 5400, while the sum is 28.

The square root of 21530656 is about 4640.1137917081. The cubic root of 21530656 is about 278.1969861386.

The spelling of 21530656 in words is "twenty-one million, five hundred thirty thousand, six hundred fifty-six".