21156841 has 2 divisors, whose sum is σ = 21156842. Its totient is φ = 21156840.

The previous prime is 21156829. The next prime is 21156847. The reversal of 21156841 is 14865112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15178816 + 5978025 = 3896^2 + 2445^2 .

It is a cyclic number.

It is not a de Polignac number, because 21156841 - 2⁵ = 21156809 is a prime.

It is a super-2 number, since 2×21156841² = 895223842198562, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21156847) by changing a digit.

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

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10578420 + 10578421.

It is an arithmetic number, because the mean of its divisors is an integer number (10578421).

Almost surely, 2^21156841 is an apocalyptic number.

It is an amenable number.

21156841 is a deficient number, since it is larger than the sum of its proper divisors (1).

21156841 is an equidigital number, since it uses as much as digits as its factorization.

21156841 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1920, while the sum is 28.

The square root of 21156841 is about 4599.6566176183. The cubic root of 21156841 is about 276.5775598915.

The spelling of 21156841 in words is "twenty-one million, one hundred fifty-six thousand, eight hundred forty-one".