20513257 has 2 divisors, whose sum is σ = 20513258. Its totient is φ = 20513256.

The previous prime is 20513231. The next prime is 20513261. The reversal of 20513257 is 75231502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13980121 + 6533136 = 3739^2 + 2556^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20513257 is a prime.

It is not a weakly prime, because it can be changed into another prime (20513267) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10256628 + 10256629.

It is an arithmetic number, because the mean of its divisors is an integer number (10256629).

Almost surely, 2^20513257 is an apocalyptic number.

It is an amenable number.

20513257 is a deficient number, since it is larger than the sum of its proper divisors (1).

20513257 is an equidigital number, since it uses as much as digits as its factorization.

20513257 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2100, while the sum is 25.

The square root of 20513257 is about 4529.1563232019. The cubic root of 20513257 is about 273.7441668725.

Adding to 20513257 its reverse (75231502), we get a palindrome (95744759).

The spelling of 20513257 in words is "twenty million, five hundred thirteen thousand, two hundred fifty-seven".