21388320 has 96 divisors (see below), whose sum is σ = 74874240. Its totient is φ = 5702400.

The previous prime is 21388313. The next prime is 21388327. The reversal of 21388320 is 2388312.

It is an interprime number because it is at equal distance from previous prime (21388313) and next prime (21388327).

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21388327) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1845 + ... + 6795.

It is an arithmetic number, because the mean of its divisors is an integer number (779940).

Almost surely, 2^21388320 is an apocalyptic number.

21388320 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 21388320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37437120).

21388320 is an abundant number, since it is smaller than the sum of its proper divisors (53485920).

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

21388320 is a wasteful number, since it uses less digits than its factorization.

21388320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4975 (or 4961 counting only the distinct ones).

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

The square root of 21388320 is about 4624.7508040974. The cubic root of 21388320 is about 277.5825904642.

The spelling of 21388320 in words is "twenty-one million, three hundred eighty-eight thousand, three hundred twenty".