21538841 has 2 divisors, whose sum is σ = 21538842. Its totient is φ = 21538840.

The previous prime is 21538789. The next prime is 21538843. The reversal of 21538841 is 14883512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18966025 + 2572816 = 4355^2 + 1604^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21538841 is a prime.

Together with 21538843, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21538798 and 21538807.

It is not a weakly prime, because it can be changed into another prime (21538843) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10769420 + 10769421.

It is an arithmetic number, because the mean of its divisors is an integer number (10769421).

Almost surely, 2^21538841 is an apocalyptic number.

It is an amenable number.

21538841 is a deficient number, since it is larger than the sum of its proper divisors (1).

21538841 is an equidigital number, since it uses as much as digits as its factorization.

21538841 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7680, while the sum is 32.

The square root of 21538841 is about 4640.9956905819. The cubic root of 21538841 is about 278.2322343888.

The spelling of 21538841 in words is "twenty-one million, five hundred thirty-eight thousand, eight hundred forty-one".