256513121 has 2 divisors, whose sum is σ = 256513122. Its totient is φ = 256513120.

The previous prime is 256513099. The next prime is 256513123. The reversal of 256513121 is 121315652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 246144721 + 10368400 = 15689^2 + 3220^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-256513121 is a prime.

Together with 256513123, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (256513123) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128256560 + 128256561.

It is an arithmetic number, because the mean of its divisors is an integer number (128256561).

Almost surely, 2^256513121 is an apocalyptic number.

It is an amenable number.

256513121 is a deficient number, since it is larger than the sum of its proper divisors (1).

256513121 is an equidigital number, since it uses as much as digits as its factorization.

256513121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1800, while the sum is 26.

The square root of 256513121 is about 16016.0270042230. The cubic root of 256513121 is about 635.3843714187.

Adding to 256513121 its reverse (121315652), we get a palindrome (377828773).

The spelling of 256513121 in words is "two hundred fifty-six million, five hundred thirteen thousand, one hundred twenty-one".