1278338721 has 16 divisors (see below), whose sum is σ = 1860288768. Its totient is φ = 774381200.

The previous prime is 1278338687. The next prime is 1278338731.

1278338721 is nontrivially palindromic in base 10.

It is a cyclic number.

It is not a de Polignac number, because 1278338721 - 2⁹ = 1278338209 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1278338731) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 71530 + ... + 87596.

It is an arithmetic number, because the mean of its divisors is an integer number (116268048).

Almost surely, 2^1278338721 is an apocalyptic number.

1278338721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1278338721 is a deficient number, since it is larger than the sum of its proper divisors (581950047).

1278338721 is a wasteful number, since it uses less digits than its factorization.

1278338721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18492.

The product of its digits is 112896, while the sum is 42.

The square root of 1278338721 is about 35753.8630220568. The cubic root of 1278338721 is about 1085.2971135888.

The spelling of 1278338721 in words is "one billion, two hundred seventy-eight million, three hundred thirty-eight thousand, seven hundred twenty-one".