21243907 has 2 divisors, whose sum is σ = 21243908. Its totient is φ = 21243906.

The previous prime is 21243857. The next prime is 21243913. The reversal of 21243907 is 70934212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21243907 - 2⁷ = 21243779 is a prime.

It is equal to p_1344349 and since 21243907 and 1344349 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21243977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621953 + 10621954.

It is an arithmetic number, because the mean of its divisors is an integer number (10621954).

Almost surely, 2^21243907 is an apocalyptic number.

21243907 is a deficient number, since it is larger than the sum of its proper divisors (1).

21243907 is an equidigital number, since it uses as much as digits as its factorization.

21243907 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3024, while the sum is 28.

The square root of 21243907 is about 4609.1113026266. Note that the first 3 decimals coincide. The cubic root of 21243907 is about 276.9564372579.

The spelling of 21243907 in words is "twenty-one million, two hundred forty-three thousand, nine hundred seven".