20516309 has 4 divisors (see below), whose sum is σ = 22381440. Its totient is φ = 18651180.

The previous prime is 20516281. The next prime is 20516323. The reversal of 20516309 is 90361502.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20516309 - 2¹² = 20512213 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20516009) 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 in 3 ways as a sum of consecutive naturals, for example, 932549 + ... + 932570.

It is an arithmetic number, because the mean of its divisors is an integer number (5595360).

Almost surely, 2^20516309 is an apocalyptic number.

It is an amenable number.

20516309 is a deficient number, since it is larger than the sum of its proper divisors (1865131).

20516309 is a wasteful number, since it uses less digits than its factorization.

20516309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1865130.

The product of its (nonzero) digits is 1620, while the sum is 26.

The square root of 20516309 is about 4529.4932387630. The cubic root of 20516309 is about 273.7577422523.

The spelling of 20516309 in words is "twenty million, five hundred sixteen thousand, three hundred nine".