21037609 has 2 divisors, whose sum is σ = 21037610. Its totient is φ = 21037608.

The previous prime is 21037607. The next prime is 21037631. The reversal of 21037609 is 90673012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17808400 + 3229209 = 4220^2 + 1797^2 .

It is a cyclic number.

It is not a de Polignac number, because 21037609 - 2¹ = 21037607 is a prime.

Together with 21037607, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21037603) 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, 10518804 + 10518805.

It is an arithmetic number, because the mean of its divisors is an integer number (10518805).

Almost surely, 2^21037609 is an apocalyptic number.

It is an amenable number.

21037609 is a deficient number, since it is larger than the sum of its proper divisors (1).

21037609 is an equidigital number, since it uses as much as digits as its factorization.

21037609 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2268, while the sum is 28.

The square root of 21037609 is about 4586.6773376814. The cubic root of 21037609 is about 276.0570184306.

The spelling of 21037609 in words is "twenty-one million, thirty-seven thousand, six hundred nine".