21423959 has 2 divisors, whose sum is σ = 21423960. Its totient is φ = 21423958.

The previous prime is 21423917. The next prime is 21423977. The reversal of 21423959 is 95932412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21423959 - 2²⁴ = 4646743 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21423979) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10711979 + 10711980.

It is an arithmetic number, because the mean of its divisors is an integer number (10711980).

Almost surely, 2^21423959 is an apocalyptic number.

21423959 is a deficient number, since it is larger than the sum of its proper divisors (1).

21423959 is an equidigital number, since it uses as much as digits as its factorization.

21423959 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 19440, while the sum is 35.

The square root of 21423959 is about 4628.6022728249. The cubic root of 21423959 is about 277.7366819856.

The spelling of 21423959 in words is "twenty-one million, four hundred twenty-three thousand, nine hundred fifty-nine".