1278668721 has 16 divisors (see below), whose sum is σ = 1862138880. Its totient is φ = 774010320.

The previous prime is 1278668711. The next prime is 1278668747.

1278668721 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 1278668721 - 2⁵ = 1278668689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1278668711) 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, 4596 + ... + 50778.

It is an arithmetic number, because the mean of its divisors is an integer number (116383680).

Almost surely, 2^1278668721 is an apocalyptic number.

1278668721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1278668721 is a deficient number, since it is larger than the sum of its proper divisors (583470159).

1278668721 is a wasteful number, since it uses less digits than its factorization.

1278668721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47036.

The product of its digits is 451584, while the sum is 48.

The square root of 1278668721 is about 35758.4776102115. The cubic root of 1278668721 is about 1085.3904944817.

The spelling of 1278668721 in words is "one billion, two hundred seventy-eight million, six hundred sixty-eight thousand, seven hundred twenty-one".