20513251309 has 2 divisors, whose sum is σ = 20513251310. Its totient is φ = 20513251308.

The previous prime is 20513251307. The next prime is 20513251313. The reversal of 20513251309 is 90315231502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20049710409 + 463540900 = 141597^2 + 21530^2 .

It is a cyclic number.

It is not a de Polignac number, because 20513251309 - 2¹ = 20513251307 is a prime.

Together with 20513251307, 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 (20513251301) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10256625654 + 10256625655.

It is an arithmetic number, because the mean of its divisors is an integer number (10256625655).

Almost surely, 2^20513251309 is an apocalyptic number.

It is an amenable number.

20513251309 is a deficient number, since it is larger than the sum of its proper divisors (1).

20513251309 is an equidigital number, since it uses as much as digits as its factorization.

20513251309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8100, while the sum is 31.

The spelling of 20513251309 in words is "twenty billion, five hundred thirteen million, two hundred fifty-one thousand, three hundred nine".