21812429 has 2 divisors, whose sum is σ = 21812430. Its totient is φ = 21812428.

The previous prime is 21812419. The next prime is 21812447. The reversal of 21812429 is 92421812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20043529 + 1768900 = 4477^2 + 1330^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21812429 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21812419) 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, 10906214 + 10906215.

It is an arithmetic number, because the mean of its divisors is an integer number (10906215).

Almost surely, 2^21812429 is an apocalyptic number.

It is an amenable number.

21812429 is a deficient number, since it is larger than the sum of its proper divisors (1).

21812429 is an equidigital number, since it uses as much as digits as its factorization.

21812429 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2304, while the sum is 29.

The square root of 21812429 is about 4670.3778219754. The cubic root of 21812429 is about 279.4053237792.

The spelling of 21812429 in words is "twenty-one million, eight hundred twelve thousand, four hundred twenty-nine".