16521709 has 2 divisors, whose sum is σ = 16521710. Its totient is φ = 16521708.

The previous prime is 16521707. The next prime is 16521727. The reversal of 16521709 is 90712561.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15824484 + 697225 = 3978^2 + 835^2 .

It is a cyclic number.

It is not a de Polignac number, because 16521709 - 2¹ = 16521707 is a prime.

Together with 16521707, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16521707) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8260854 + 8260855.

It is an arithmetic number, because the mean of its divisors is an integer number (8260855).

Almost surely, 2^16521709 is an apocalyptic number.

It is an amenable number.

16521709 is a deficient number, since it is larger than the sum of its proper divisors (1).

16521709 is an equidigital number, since it uses as much as digits as its factorization.

16521709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3780, while the sum is 31.

The square root of 16521709 is about 4064.6905171243. The cubic root of 16521709 is about 254.6937705483.

The spelling of 16521709 in words is "sixteen million, five hundred twenty-one thousand, seven hundred nine".