21381248 has 64 divisors (see below), whose sum is σ = 49776000. Its totient is φ = 9144576.

The previous prime is 21381211. The next prime is 21381259. The reversal of 21381248 is 84218312.

It is a tau number, because it is divible by the number of its divisors (64).

It is a self number, because there is not a number n which added to its sum of digits gives 21381248.

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, 43661 + ... + 44147.

It is an arithmetic number, because the mean of its divisors is an integer number (777750).

Almost surely, 2^21381248 is an apocalyptic number.

21381248 is a gapful number since it is divisible by the number (28) 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 21381248, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24888000).

21381248 is an abundant number, since it is smaller than the sum of its proper divisors (28394752).

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

21381248 is an frugal number, since it uses more digits than its factorization.

21381248 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 522 (or 496 counting only the distinct ones).

The product of its digits is 3072, while the sum is 29.

The square root of 21381248 is about 4623.9861591488. The cubic root of 21381248 is about 277.5519930715.

The spelling of 21381248 in words is "twenty-one million, three hundred eighty-one thousand, two hundred forty-eight".