21388118 has 4 divisors (see below), whose sum is σ = 32082180. Its totient is φ = 10694058.

The previous prime is 21388117. The next prime is 21388139. The reversal of 21388118 is 81188312.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388117) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5347028 + ... + 5347031.

It is an arithmetic number, because the mean of its divisors is an integer number (8020545).

Almost surely, 2^21388118 is an apocalyptic number.

21388118 is a deficient number, since it is larger than the sum of its proper divisors (10694062).

21388118 is a wasteful number, since it uses less digits than its factorization.

21388118 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10694061.

The product of its digits is 3072, while the sum is 32.

The square root of 21388118 is about 4624.7289650314. The cubic root of 21388118 is about 277.5817165938.

The spelling of 21388118 in words is "twenty-one million, three hundred eighty-eight thousand, one hundred eighteen".