21388117 has 2 divisors, whose sum is σ = 21388118. Its totient is φ = 21388116.

The previous prime is 21388099. The next prime is 21388139. The reversal of 21388117 is 71188312.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20439441 + 948676 = 4521^2 + 974^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21388117 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21388177) 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, 10694058 + 10694059.

It is an arithmetic number, because the mean of its divisors is an integer number (10694059).

Almost surely, 2^21388117 is an apocalyptic number.

It is an amenable number.

21388117 is a deficient number, since it is larger than the sum of its proper divisors (1).

21388117 is an equidigital number, since it uses as much as digits as its factorization.

21388117 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2688, while the sum is 31.

The square root of 21388117 is about 4624.7288569169. The cubic root of 21388117 is about 277.5817122677.

The spelling of 21388117 in words is "twenty-one million, three hundred eighty-eight thousand, one hundred seventeen".