21752609 has 2 divisors, whose sum is σ = 21752610. Its totient is φ = 21752608.

The previous prime is 21752603. The next prime is 21752611. The reversal of 21752609 is 90625712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20070400 + 1682209 = 4480^2 + 1297^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21752609 is a prime.

It is a Sophie Germain prime.

Together with 21752611, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21752603) 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, 10876304 + 10876305.

It is an arithmetic number, because the mean of its divisors is an integer number (10876305).

Almost surely, 2^21752609 is an apocalyptic number.

It is an amenable number.

21752609 is a deficient number, since it is larger than the sum of its proper divisors (1).

21752609 is an equidigital number, since it uses as much as digits as its factorization.

21752609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7560, while the sum is 32.

The square root of 21752609 is about 4663.9692323170. The cubic root of 21752609 is about 279.1496693990.

The spelling of 21752609 in words is "twenty-one million, seven hundred fifty-two thousand, six hundred nine".