278878221 has 14 divisors (see below), whose sum is σ = 418127150. Its totient is φ = 185918328.

The previous prime is 278878199. The next prime is 278878231. The reversal of 278878221 is 122878872.

It can be written as a sum of positive squares in only one way, i.e., 278422596 + 455625 = 16686^2 + 675^2 .

It is not a de Polignac number, because 278878221 - 2¹⁵ = 278845453 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (278878231) 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 in 13 ways as a sum of consecutive naturals, for example, 190546 + ... + 192003.

It is an arithmetic number, because the mean of its divisors is an integer number (29866225).

Almost surely, 2^278878221 is an apocalyptic number.

It is an amenable number.

278878221 is a deficient number, since it is larger than the sum of its proper divisors (139248929).

278878221 is an frugal number, since it uses more digits than its factorization.

278878221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 382567 (or 382552 counting only the distinct ones).

The product of its digits is 200704, while the sum is 45.

The square root of 278878221 is about 16699.6473316055. The cubic root of 278878221 is about 653.3384228108.

The spelling of 278878221 in words is "two hundred seventy-eight million, eight hundred seventy-eight thousand, two hundred twenty-one".