1278421891778 has 16 divisors (see below), whose sum is σ = 1919507812920. Its totient is φ = 638586247296.

The previous prime is 1278421891759. The next prime is 1278421891841. The reversal of 1278421891778 is 8771981248721.

It can be written as a sum of positive squares in 4 ways, for example, as 1264291101649 + 14130790129 = 1124407^2 + 118873^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8918126 + ... + 9060342.

Almost surely, 2^{1278421891778} is an apocalyptic number.

1278421891778 is a deficient number, since it is larger than the sum of its proper divisors (641085921142).

1278421891778 is a wasteful number, since it uses less digits than its factorization.

1278421891778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 146581.

The product of its digits is 25288704, while the sum is 65.

The spelling of 1278421891778 in words is "one trillion, two hundred seventy-eight billion, four hundred twenty-one million, eight hundred ninety-one thousand, seven hundred seventy-eight".