1278972385921 has 4 divisors (see below), whose sum is σ = 1278979317252. Its totient is φ = 1278965454592.

The previous prime is 1278972385907. The next prime is 1278972385961. The reversal of 1278972385921 is 1295832798721.

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 890967975921 + 388004410000 = 943911^2 + 622900^2 .

It is a cyclic number.

It is not a de Polignac number, because 1278972385921 - 2²⁹ = 1278435515009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1278972385961) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3181096 + ... + 3560521.

It is an arithmetic number, because the mean of its divisors is an integer number (319744829313).

Almost surely, 2^{1278972385921} is an apocalyptic number.

It is an amenable number.

1278972385921 is a deficient number, since it is larger than the sum of its proper divisors (6931331).

1278972385921 is an equidigital number, since it uses as much as digits as its factorization.

1278972385921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6931330.

The product of its digits is 30481920, while the sum is 64.

The spelling of 1278972385921 in words is "one trillion, two hundred seventy-eight billion, nine hundred seventy-two million, three hundred eighty-five thousand, nine hundred twenty-one".