21556841 has 2 divisors, whose sum is σ = 21556842. Its totient is φ = 21556840.

The previous prime is 21556783. The next prime is 21556859. The reversal of 21556841 is 14865512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17472400 + 4084441 = 4180^2 + 2021^2 .

It is a cyclic number.

It is not a de Polignac number, because 21556841 - 2¹⁰ = 21555817 is a prime.

It is equal to p_1362929 and since 21556841 and 1362929 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 21556798 and 21556807.

It is not a weakly prime, because it can be changed into another prime (21556891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10778420 + 10778421.

It is an arithmetic number, because the mean of its divisors is an integer number (10778421).

Almost surely, 2^21556841 is an apocalyptic number.

It is an amenable number.

21556841 is a deficient number, since it is larger than the sum of its proper divisors (1).

21556841 is an equidigital number, since it uses as much as digits as its factorization.

21556841 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9600, while the sum is 32.

The square root of 21556841 is about 4642.9345246299. The cubic root of 21556841 is about 278.3097189937.

The spelling of 21556841 in words is "twenty-one million, five hundred fifty-six thousand, eight hundred forty-one".