21243841 has 2 divisors, whose sum is σ = 21243842. Its totient is φ = 21243840.

The previous prime is 21243823. The next prime is 21243857. The reversal of 21243841 is 14834212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20793600 + 450241 = 4560^2 + 671^2 .

It is a cyclic number.

It is not a de Polignac number, because 21243841 - 2⁷ = 21243713 is a prime.

It is not a weakly prime, because it can be changed into another prime (21243821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621920 + 10621921.

It is an arithmetic number, because the mean of its divisors is an integer number (10621921).

Almost surely, 2^21243841 is an apocalyptic number.

It is an amenable number.

21243841 is a deficient number, since it is larger than the sum of its proper divisors (1).

21243841 is an equidigital number, since it uses as much as digits as its factorization.

21243841 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1536, while the sum is 25.

The square root of 21243841 is about 4609.1041428894. The cubic root of 21243841 is about 276.9561504440.

The spelling of 21243841 in words is "twenty-one million, two hundred forty-three thousand, eight hundred forty-one".