278323261 has 2 divisors, whose sum is σ = 278323262. Its totient is φ = 278323260.

The previous prime is 278323259. The next prime is 278323291. The reversal of 278323261 is 162323872.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 223652025 + 54671236 = 14955^2 + 7394^2 .

It is a cyclic number.

It is not a de Polignac number, because 278323261 - 2¹ = 278323259 is a prime.

It is a super-2 number, since 2×278323261² = 154927675227348242, which contains 22 as substring.

Together with 278323259, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (278323291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 139161630 + 139161631.

It is an arithmetic number, because the mean of its divisors is an integer number (139161631).

Almost surely, 2^278323261 is an apocalyptic number.

It is an amenable number.

278323261 is a deficient number, since it is larger than the sum of its proper divisors (1).

278323261 is an equidigital number, since it uses as much as digits as its factorization.

278323261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 24192, while the sum is 34.

The square root of 278323261 is about 16683.0231373094. The cubic root of 278323261 is about 652.9047598522.

The spelling of 278323261 in words is "two hundred seventy-eight million, three hundred twenty-three thousand, two hundred sixty-one".