21388373 has 2 divisors, whose sum is σ = 21388374. Its totient is φ = 21388372.

The previous prime is 21388333. The next prime is 21388417. The reversal of 21388373 is 37388312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11135569 + 10252804 = 3337^2 + 3202^2 .

It is a cyclic number.

It is not a de Polignac number, because 21388373 - 2⁸ = 21388117 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21388313) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10694186 + 10694187.

It is an arithmetic number, because the mean of its divisors is an integer number (10694187).

Almost surely, 2^21388373 is an apocalyptic number.

It is an amenable number.

21388373 is a deficient number, since it is larger than the sum of its proper divisors (1).

21388373 is an equidigital number, since it uses as much as digits as its factorization.

21388373 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24192, while the sum is 35.

The square root of 21388373 is about 4624.7565341324. The cubic root of 21388373 is about 277.5828197461.

The spelling of 21388373 in words is "twenty-one million, three hundred eighty-eight thousand, three hundred seventy-three".