21406529 has 2 divisors, whose sum is σ = 21406530. Its totient is φ = 21406528.

The previous prime is 21406507. The next prime is 21406531. The reversal of 21406529 is 92560412.

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., 10857025 + 10549504 = 3295^2 + 3248^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21406529 is a prime.

Together with 21406531, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21406549) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10703264 + 10703265.

It is an arithmetic number, because the mean of its divisors is an integer number (10703265).

Almost surely, 2^21406529 is an apocalyptic number.

It is an amenable number.

21406529 is a deficient number, since it is larger than the sum of its proper divisors (1).

21406529 is an equidigital number, since it uses as much as digits as its factorization.

21406529 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 21406529 is about 4626.7190318843. The cubic root of 21406529 is about 277.6613416655.

The spelling of 21406529 in words is "twenty-one million, four hundred six thousand, five hundred twenty-nine".