278791981 has 4 divisors (see below), whose sum is σ = 300237532. Its totient is φ = 257346432.

The previous prime is 278791969. The next prime is 278791991. The reversal of 278791981 is 189197872.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 46717225 + 232074756 = 6835^2 + 15234^2 .

It is a cyclic number.

It is not a de Polignac number, because 278791981 - 2¹¹ = 278789933 is a prime.

It is a super-2 number, since 2×278791981² = 155449937339808722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (278791951) 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 3 ways as a sum of consecutive naturals, for example, 10722756 + ... + 10722781.

It is an arithmetic number, because the mean of its divisors is an integer number (75059383).

Almost surely, 2^278791981 is an apocalyptic number.

It is an amenable number.

278791981 is a deficient number, since it is larger than the sum of its proper divisors (21445551).

278791981 is a wasteful number, since it uses less digits than its factorization.

278791981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21445550.

The product of its digits is 508032, while the sum is 52.

The square root of 278791981 is about 16697.0650414976. The cubic root of 278791981 is about 653.2710699781.

The spelling of 278791981 in words is "two hundred seventy-eight million, seven hundred ninety-one thousand, nine hundred eighty-one".