21637841 has 4 divisors (see below), whose sum is σ = 21699492. Its totient is φ = 21576192.

The previous prime is 21637807. The next prime is 21637849. The reversal of 21637841 is 14873612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7311616 + 14326225 = 2704^2 + 3785^2 .

It is a cyclic number.

It is not a de Polignac number, because 21637841 - 2¹⁰ = 21636817 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21637798 and 21637807.

It is not an unprimeable number, because it can be changed into a prime (21637849) 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 3 ways as a sum of consecutive naturals, for example, 30296 + ... + 31001.

It is an arithmetic number, because the mean of its divisors is an integer number (5424873).

Almost surely, 2^21637841 is an apocalyptic number.

It is an amenable number.

21637841 is a deficient number, since it is larger than the sum of its proper divisors (61651).

21637841 is an equidigital number, since it uses as much as digits as its factorization.

21637841 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61650.

The product of its digits is 8064, while the sum is 32.

The square root of 21637841 is about 4651.6492774069. The cubic root of 21637841 is about 278.6578669553.

The spelling of 21637841 in words is "twenty-one million, six hundred thirty-seven thousand, eight hundred forty-one".