256511221 has 2 divisors, whose sum is σ = 256511222. Its totient is φ = 256511220.

The previous prime is 256511053. The next prime is 256511273. The reversal of 256511221 is 122115652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 240591121 + 15920100 = 15511^2 + 3990^2 .

It is a cyclic number.

It is not a de Polignac number, because 256511221 - 2¹³ = 256503029 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256611221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128255610 + 128255611.

It is an arithmetic number, because the mean of its divisors is an integer number (128255611).

Almost surely, 2^256511221 is an apocalyptic number.

It is an amenable number.

256511221 is a deficient number, since it is larger than the sum of its proper divisors (1).

256511221 is an equidigital number, since it uses as much as digits as its factorization.

256511221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1200, while the sum is 25.

The square root of 256511221 is about 16015.9676885288. The cubic root of 256511221 is about 635.3828026447.

Adding to 256511221 its reverse (122115652), we get a palindrome (378626873).

The spelling of 256511221 in words is "two hundred fifty-six million, five hundred eleven thousand, two hundred twenty-one".