21403439 has 2 divisors, whose sum is σ = 21403440. Its totient is φ = 21403438.

The previous prime is 21403433. The next prime is 21403441. The reversal of 21403439 is 93430412.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21403439 is a prime.

It is a Sophie Germain prime.

Together with 21403441, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21403433) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10701719 + 10701720.

It is an arithmetic number, because the mean of its divisors is an integer number (10701720).

Almost surely, 2^21403439 is an apocalyptic number.

21403439 is a deficient number, since it is larger than the sum of its proper divisors (1).

21403439 is an equidigital number, since it uses as much as digits as its factorization.

21403439 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2592, while the sum is 26.

The square root of 21403439 is about 4626.3850898947. The cubic root of 21403439 is about 277.6479810247.

The spelling of 21403439 in words is "twenty-one million, four hundred three thousand, four hundred thirty-nine".