20513813 has 4 divisors (see below), whose sum is σ = 20539980. Its totient is φ = 20487648.

The previous prime is 20513791. The next prime is 20513819. The reversal of 20513813 is 31831502.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 12802084 + 7711729 = 3578^2 + 2777^2 .

It is a cyclic number.

It is not a de Polignac number, because 20513813 - 2⁸ = 20513557 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20513819) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11870 + ... + 13487.

It is an arithmetic number, because the mean of its divisors is an integer number (5134995).

Almost surely, 2^20513813 is an apocalyptic number.

It is an amenable number.

20513813 is a deficient number, since it is larger than the sum of its proper divisors (26167).

20513813 is an equidigital number, since it uses as much as digits as its factorization.

20513813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26166.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 20513813 is about 4529.2177028710. The cubic root of 20513813 is about 273.7466400761.

The spelling of 20513813 in words is "twenty million, five hundred thirteen thousand, eight hundred thirteen".