21248640 has 384 divisors, whose sum is σ = 91653120. Its totient is φ = 4423680.

The previous prime is 21248639. The next prime is 21248641. The reversal of 21248640 is 4684212.

21248640 is a `hidden beast` number, since 2 + 12 + 4 + 8 + 640 = 666.

It is an interprime number because it is at equal distance from previous prime (21248639) and next prime (21248641).

It is a tau number, because it is divible by the number of its divisors (384).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21248641) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 685425 + ... + 685455.

It is an arithmetic number, because the mean of its divisors is an integer number (238680).

Almost surely, 2^21248640 is an apocalyptic number.

21248640 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 21248640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (45826560).

21248640 is an abundant number, since it is smaller than the sum of its proper divisors (70404480).

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

21248640 is a wasteful number, since it uses less digits than its factorization.

21248640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80 (or 65 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 27.

The square root of 21248640 is about 4609.6247135748. The cubic root of 21248640 is about 276.9770037429.

The spelling of 21248640 in words is "twenty-one million, two hundred forty-eight thousand, six hundred forty".