21375439 has 2 divisors, whose sum is σ = 21375440. Its totient is φ = 21375438.

The previous prime is 21375413. The next prime is 21375457. The reversal of 21375439 is 93457312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21375439 - 2⁷ = 21375311 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21315439) 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, 10687719 + 10687720.

It is an arithmetic number, because the mean of its divisors is an integer number (10687720).

Almost surely, 2^21375439 is an apocalyptic number.

21375439 is a deficient number, since it is larger than the sum of its proper divisors (1).

21375439 is an equidigital number, since it uses as much as digits as its factorization.

21375439 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 22680, while the sum is 34.

The square root of 21375439 is about 4623.3579787855. The cubic root of 21375439 is about 277.5268550695.

The spelling of 21375439 in words is "twenty-one million, three hundred seventy-five thousand, four hundred thirty-nine".