21638117 has 2 divisors, whose sum is σ = 21638118. Its totient is φ = 21638116.

The previous prime is 21638069. The next prime is 21638129. The reversal of 21638117 is 71183612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20802721 + 835396 = 4561^2 + 914^2 .

It is a cyclic number.

It is not a de Polignac number, because 21638117 - 2¹⁰ = 21637093 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21638117.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21638167) 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, 10819058 + 10819059.

It is an arithmetic number, because the mean of its divisors is an integer number (10819059).

Almost surely, 2^21638117 is an apocalyptic number.

It is an amenable number.

21638117 is a deficient number, since it is larger than the sum of its proper divisors (1).

21638117 is an equidigital number, since it uses as much as digits as its factorization.

21638117 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2016, while the sum is 29.

The square root of 21638117 is about 4651.6789442093. The cubic root of 21638117 is about 278.6590517507.

The spelling of 21638117 in words is "twenty-one million, six hundred thirty-eight thousand, one hundred seventeen".