21605429 has 2 divisors, whose sum is σ = 21605430. Its totient is φ = 21605428.

The previous prime is 21605417. The next prime is 21605459. The reversal of 21605429 is 92450612.

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., 14326225 + 7279204 = 3785^2 + 2698^2 .

It is a cyclic number.

It is not a de Polignac number, because 21605429 - 2⁸ = 21605173 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21605459) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10802714 + 10802715.

It is an arithmetic number, because the mean of its divisors is an integer number (10802715).

Almost surely, 2^21605429 is an apocalyptic number.

It is an amenable number.

21605429 is a deficient number, since it is larger than the sum of its proper divisors (1).

21605429 is an equidigital number, since it uses as much as digits as its factorization.

21605429 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 21605429 is about 4648.1640461584. The cubic root of 21605429 is about 278.5186606416.

The spelling of 21605429 in words is "twenty-one million, six hundred five thousand, four hundred twenty-nine".