21388768 has 24 divisors (see below), whose sum is σ = 42621768. Its totient is φ = 10564224.

The previous prime is 21388751. The next prime is 21388769. The reversal of 21388768 is 86788312.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388769) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1371 + ... + 6682.

It is an arithmetic number, because the mean of its divisors is an integer number (1775907).

Almost surely, 2^21388768 is an apocalyptic number.

It is an amenable number.

21388768 is a deficient number, since it is larger than the sum of its proper divisors (21233000).

21388768 is an equidigital number, since it uses as much as digits as its factorization.

21388768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8146 (or 8138 counting only the distinct ones).

The product of its digits is 129024, while the sum is 43.

The square root of 21388768 is about 4624.7992388859. The cubic root of 21388768 is about 277.5845285334.

The spelling of 21388768 in words is "twenty-one million, three hundred eighty-eight thousand, seven hundred sixty-eight".