278417261 has 2 divisors, whose sum is σ = 278417262. Its totient is φ = 278417260.

The previous prime is 278417239. The next prime is 278417263. The reversal of 278417261 is 162714872.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 256608361 + 21808900 = 16019^2 + 4670^2 .

It is a cyclic number.

It is not a de Polignac number, because 278417261 - 2²⁶ = 211308397 is a prime.

Together with 278417263, 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 (278417263) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 139208630 + 139208631.

It is an arithmetic number, because the mean of its divisors is an integer number (139208631).

Almost surely, 2^278417261 is an apocalyptic number.

It is an amenable number.

278417261 is a deficient number, since it is larger than the sum of its proper divisors (1).

278417261 is an equidigital number, since it uses as much as digits as its factorization.

278417261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 37632, while the sum is 38.

The square root of 278417261 is about 16685.8401346771. The cubic root of 278417261 is about 652.9782548943.

The spelling of 278417261 in words is "two hundred seventy-eight million, four hundred seventeen thousand, two hundred sixty-one".