278997261561 has 6 divisors (see below), whose sum is σ = 402996044490. Its totient is φ = 185998174368.

The previous prime is 278997261559. The next prime is 278997261617. The reversal of 278997261561 is 165162799872.

278997261561 is a `hidden beast` number, since 2 + 7 + 8 + 9 + 9 + 7 + 2 + 61 + 561 = 666.

It can be written as a sum of positive squares in only one way, i.e., 270857793600 + 8139467961 = 520440^2 + 90219^2 .

It is not a de Polignac number, because 278997261561 - 2¹ = 278997261559 is a prime.

It is not an unprimeable number, because it can be changed into a prime (278997261161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 15499847856 + ... + 15499847873.

It is an arithmetic number, because the mean of its divisors is an integer number (67166007415).

Almost surely, 2^278997261561 is an apocalyptic number.

It is an amenable number.

278997261561 is a deficient number, since it is larger than the sum of its proper divisors (123998782929).

278997261561 is a wasteful number, since it uses less digits than its factorization.

278997261561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30999695735 (or 30999695732 counting only the distinct ones).

The product of its digits is 22861440, while the sum is 63.

The spelling of 278997261561 in words is "two hundred seventy-eight billion, nine hundred ninety-seven million, two hundred sixty-one thousand, five hundred sixty-one".