278391257 has 2 divisors, whose sum is σ = 278391258. Its totient is φ = 278391256.

The previous prime is 278391247. The next prime is 278391259. The reversal of 278391257 is 752193872.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 263867536 + 14523721 = 16244^2 + 3811^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-278391257 is a prime.

Together with 278391259, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (278391259) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 139195628 + 139195629.

It is an arithmetic number, because the mean of its divisors is an integer number (139195629).

Almost surely, 2^278391257 is an apocalyptic number.

It is an amenable number.

278391257 is a deficient number, since it is larger than the sum of its proper divisors (1).

278391257 is an equidigital number, since it uses as much as digits as its factorization.

278391257 is an evil number, because the sum of its binary digits is even.

The product of its digits is 211680, while the sum is 44.

The square root of 278391257 is about 16685.0608929066. The cubic root of 278391257 is about 652.9579250063.

The spelling of 278391257 in words is "two hundred seventy-eight million, three hundred ninety-one thousand, two hundred fifty-seven".