21409429 has 2 divisors, whose sum is σ = 21409430. Its totient is φ = 21409428.

The previous prime is 21409417. The next prime is 21409457. The reversal of 21409429 is 92490412.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18922500 + 2486929 = 4350^2 + 1577^2 .

It is a cyclic number.

It is not a de Polignac number, because 21409429 - 2⁵ = 21409397 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21409429.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21409469) 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, 10704714 + 10704715.

It is an arithmetic number, because the mean of its divisors is an integer number (10704715).

Almost surely, 2^21409429 is an apocalyptic number.

It is an amenable number.

21409429 is a deficient number, since it is larger than the sum of its proper divisors (1).

21409429 is an equidigital number, since it uses as much as digits as its factorization.

21409429 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 21409429 is about 4627.0324183001. The cubic root of 21409429 is about 277.6738796086.

The spelling of 21409429 in words is "twenty-one million, four hundred nine thousand, four hundred twenty-nine".