256161221 has 2 divisors, whose sum is σ = 256161222. Its totient is φ = 256161220.

The previous prime is 256161203. The next prime is 256161223. The reversal of 256161221 is 122161652.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 214300321 + 41860900 = 14639^2 + 6470^2 .

It is a cyclic number.

It is not a de Polignac number, because 256161221 - 2¹⁰ = 256160197 is a prime.

It is a super-2 number, since 2×256161221² = 131237142288421682, which contains 22 as substring.

Together with 256161223, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (256161223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 128080610 + 128080611.

It is an arithmetic number, because the mean of its divisors is an integer number (128080611).

Almost surely, 2^256161221 is an apocalyptic number.

It is an amenable number.

256161221 is a deficient number, since it is larger than the sum of its proper divisors (1).

256161221 is an equidigital number, since it uses as much as digits as its factorization.

256161221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1440, while the sum is 26.

The square root of 256161221 is about 16005.0373632803. The cubic root of 256161221 is about 635.0936857246.

The spelling of 256161221 in words is "two hundred fifty-six million, one hundred sixty-one thousand, two hundred twenty-one".