21238429 has 2 divisors, whose sum is σ = 21238430. Its totient is φ = 21238428.

The previous prime is 21238363. The next prime is 21238433. The reversal of 21238429 is 92483212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21178404 + 60025 = 4602^2 + 245^2 .

It is a cyclic number.

It is not a de Polignac number, because 21238429 - 2⁹ = 21237917 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21238429.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21238229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10619214 + 10619215.

It is an arithmetic number, because the mean of its divisors is an integer number (10619215).

Almost surely, 2^21238429 is an apocalyptic number.

It is an amenable number.

21238429 is a deficient number, since it is larger than the sum of its proper divisors (1).

21238429 is an equidigital number, since it uses as much as digits as its factorization.

21238429 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6912, while the sum is 31.

The square root of 21238429 is about 4608.5170065868. The cubic root of 21238429 is about 276.9326296819.

The spelling of 21238429 in words is "twenty-one million, two hundred thirty-eight thousand, four hundred twenty-nine".