21529609 has 2 divisors, whose sum is σ = 21529610. Its totient is φ = 21529608.

The previous prime is 21529561. The next prime is 21529621. The reversal of 21529609 is 90692512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21529600 + 9 = 4640^2 + 3^2 .

It is a cyclic number.

It is not a de Polignac number, because 21529609 - 2⁷ = 21529481 is a prime.

It is not a weakly prime, because it can be changed into another prime (21529639) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10764804 + 10764805.

It is an arithmetic number, because the mean of its divisors is an integer number (10764805).

Almost surely, 2^21529609 is an apocalyptic number.

It is an amenable number.

21529609 is a deficient number, since it is larger than the sum of its proper divisors (1).

21529609 is an equidigital number, since it uses as much as digits as its factorization.

21529609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9720, while the sum is 34.

The square root of 21529609 is about 4640.0009698275. Note that the first 3 decimals coincide. The cubic root of 21529609 is about 278.1924766465.

The spelling of 21529609 in words is "twenty-one million, five hundred twenty-nine thousand, six hundred nine".