21001841 has 12 divisors (see below), whose sum is σ = 24653412. Its totient is φ = 17837568.

The previous prime is 21001837. The next prime is 21001843. The reversal of 21001841 is 14810012.

It can be written as a sum of positive squares in 2 ways, for example, as 1677025 + 19324816 = 1295^2 + 4396^2 .

It is not a de Polignac number, because 21001841 - 2² = 21001837 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21001843) 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 in 11 ways as a sum of consecutive naturals, for example, 3641 + ... + 7433.

It is an arithmetic number, because the mean of its divisors is an integer number (2054451).

Almost surely, 2^21001841 is an apocalyptic number.

It is an amenable number.

21001841 is a deficient number, since it is larger than the sum of its proper divisors (3651571).

21001841 is a wasteful number, since it uses less digits than its factorization.

21001841 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3920 (or 3913 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 17.

The square root of 21001841 is about 4582.7765601216. The cubic root of 21001841 is about 275.9004795921.

Adding to 21001841 its reverse (14810012), we get a palindrome (35811853).

The spelling of 21001841 in words is "twenty-one million, one thousand, eight hundred forty-one".