21213648 has 60 divisors (see below), whose sum is σ = 59772960. Its totient is φ = 7023168.

The previous prime is 21213631. The next prime is 21213667. The reversal of 21213648 is 84631212.

21213648 is a `hidden beast` number, since 2 + 1 + 2 + 13 + 648 = 666.

It is a super-2 number, since 2×21213648² = 900037722935808, which contains 22 as substring.

It is a nude number because it is divisible by every one of its digits.

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 11 ways as a sum of consecutive naturals, for example, 25365 + ... + 26187.

It is an arithmetic number, because the mean of its divisors is an integer number (996216).

Almost surely, 2^21213648 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 21213648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29886480).

21213648 is an abundant number, since it is smaller than the sum of its proper divisors (38559312).

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

21213648 is a wasteful number, since it uses less digits than its factorization.

21213648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1016 (or 1007 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 21213648 is about 4605.8276129269. The cubic root of 21213648 is about 276.8248794281.

The spelling of 21213648 in words is "twenty-one million, two hundred thirteen thousand, six hundred forty-eight".