21438913 has 2 divisors, whose sum is σ = 21438914. Its totient is φ = 21438912.

The previous prime is 21438881. The next prime is 21438931. The reversal of 21438913 is 31983412.

Together with next prime (21438931) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14379264 + 7059649 = 3792^2 + 2657^2 .

It is a cyclic number.

It is not a de Polignac number, because 21438913 - 2⁵ = 21438881 is a prime.

It is not a weakly prime, because it can be changed into another prime (21438953) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10719456 + 10719457.

It is an arithmetic number, because the mean of its divisors is an integer number (10719457).

Almost surely, 2^21438913 is an apocalyptic number.

It is an amenable number.

21438913 is a deficient number, since it is larger than the sum of its proper divisors (1).

21438913 is an equidigital number, since it uses as much as digits as its factorization.

21438913 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5184, while the sum is 31.

The square root of 21438913 is about 4630.2173815060. The cubic root of 21438913 is about 277.8012873554.

The spelling of 21438913 in words is "twenty-one million, four hundred thirty-eight thousand, nine hundred thirteen".