21838517 has 2 divisors, whose sum is σ = 21838518. Its totient is φ = 21838516.

The previous prime is 21838513. The next prime is 21838519. The reversal of 21838517 is 71583812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19307236 + 2531281 = 4394^2 + 1591^2 .

It is a cyclic number.

It is not a de Polignac number, because 21838517 - 2² = 21838513 is a prime.

Together with 21838519, it forms a pair of twin primes.

It is a Chen prime.

It is a plaindrome in base 11.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21838511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10919258 + 10919259.

It is an arithmetic number, because the mean of its divisors is an integer number (10919259).

Almost surely, 2^21838517 is an apocalyptic number.

It is an amenable number.

21838517 is a deficient number, since it is larger than the sum of its proper divisors (1).

21838517 is an equidigital number, since it uses as much as digits as its factorization.

21838517 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13440, while the sum is 35.

The square root of 21838517 is about 4673.1699091730. The cubic root of 21838517 is about 279.5166704193.

The spelling of 21838517 in words is "twenty-one million, eight hundred thirty-eight thousand, five hundred seventeen".