21356429 has 2 divisors, whose sum is σ = 21356430. Its totient is φ = 21356428.

The previous prime is 21356381. The next prime is 21356431. The reversal of 21356429 is 92465312.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21252100 + 104329 = 4610^2 + 323^2 .

It is a cyclic number.

It is not a de Polignac number, because 21356429 - 2²⁴ = 4579213 is a prime.

Together with 21356431, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21356395 and 21356404.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21356459) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10678214 + 10678215.

It is an arithmetic number, because the mean of its divisors is an integer number (10678215).

Almost surely, 2^21356429 is an apocalyptic number.

It is an amenable number.

21356429 is a deficient number, since it is larger than the sum of its proper divisors (1).

21356429 is an equidigital number, since it uses as much as digits as its factorization.

21356429 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12960, while the sum is 32.

The square root of 21356429 is about 4621.3016564600. The cubic root of 21356429 is about 277.4445588997. Note that the first 3 decimals are identical.

The spelling of 21356429 in words is "twenty-one million, three hundred fifty-six thousand, four hundred twenty-nine".