21434639 has 2 divisors, whose sum is σ = 21434640. Its totient is φ = 21434638.

The previous prime is 21434591. The next prime is 21434657. The reversal of 21434639 is 93643412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21434639 - 2⁸ = 21434383 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21434669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10717319 + 10717320.

It is an arithmetic number, because the mean of its divisors is an integer number (10717320).

Almost surely, 2^21434639 is an apocalyptic number.

21434639 is a deficient number, since it is larger than the sum of its proper divisors (1).

21434639 is an equidigital number, since it uses as much as digits as its factorization.

21434639 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 32.

The square root of 21434639 is about 4629.7558250949. The cubic root of 21434639 is about 277.7828255735.

The spelling of 21434639 in words is "twenty-one million, four hundred thirty-four thousand, six hundred thirty-nine".