21105641 has 2 divisors, whose sum is σ = 21105642. Its totient is φ = 21105640.

The previous prime is 21105587. The next prime is 21105659. The reversal of 21105641 is 14650112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20894041 + 211600 = 4571^2 + 460^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21105641 is a prime.

It is not a weakly prime, because it can be changed into another prime (21105661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552820 + 10552821.

It is an arithmetic number, because the mean of its divisors is an integer number (10552821).

Almost surely, 2^21105641 is an apocalyptic number.

It is an amenable number.

21105641 is a deficient number, since it is larger than the sum of its proper divisors (1).

21105641 is an equidigital number, since it uses as much as digits as its factorization.

21105641 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 240, while the sum is 20.

The square root of 21105641 is about 4594.0876134440. The cubic root of 21105641 is about 276.3542718375.

Adding to 21105641 its reverse (14650112), we get a palindrome (35755753).

The spelling of 21105641 in words is "twenty-one million, one hundred five thousand, six hundred forty-one".