21408529 has 2 divisors, whose sum is σ = 21408530. Its totient is φ = 21408528.

The previous prime is 21408521. The next prime is 21408557. The reversal of 21408529 is 92580412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19580625 + 1827904 = 4425^2 + 1352^2 .

It is a cyclic number.

It is not a de Polignac number, because 21408529 - 2³ = 21408521 is a prime.

It is a super-2 number, since 2×21408529² = 916650227887682, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21408529.

It is not a weakly prime, because it can be changed into another prime (21408521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10704264 + 10704265.

It is an arithmetic number, because the mean of its divisors is an integer number (10704265).

Almost surely, 2^21408529 is an apocalyptic number.

It is an amenable number.

21408529 is a deficient number, since it is larger than the sum of its proper divisors (1).

21408529 is an equidigital number, since it uses as much as digits as its factorization.

21408529 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5760, while the sum is 31.

The square root of 21408529 is about 4626.9351627184. The cubic root of 21408529 is about 277.6699886440.

The spelling of 21408529 in words is "twenty-one million, four hundred eight thousand, five hundred twenty-nine".