278558561 has 2 divisors, whose sum is σ = 278558562. Its totient is φ = 278558560.

The previous prime is 278558509. The next prime is 278558569. The reversal of 278558561 is 165855872.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 214798336 + 63760225 = 14656^2 + 7985^2 .

It is a cyclic number.

It is not a de Polignac number, because 278558561 - 2²⁶ = 211449697 is a prime.

It is not a weakly prime, because it can be changed into another prime (278558569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 139279280 + 139279281.

It is an arithmetic number, because the mean of its divisors is an integer number (139279281).

Almost surely, 2^278558561 is an apocalyptic number.

It is an amenable number.

278558561 is a deficient number, since it is larger than the sum of its proper divisors (1).

278558561 is an equidigital number, since it uses as much as digits as its factorization.

278558561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 672000, while the sum is 47.

The square root of 278558561 is about 16690.0737266197. The cubic root of 278558561 is about 653.0887009000.

The spelling of 278558561 in words is "two hundred seventy-eight million, five hundred fifty-eight thousand, five hundred sixty-one".