1278959689921 has 15 divisors (see below), whose sum is σ = 1328502829665. Its totient is φ = 1231222805700.

The previous prime is 1278959689883. The next prime is 1278959689949. The reversal of 1278959689921 is 1299869598721.

The square root of 1278959689921 is 1130911.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 1278959689921 - 2¹³ = 1278959681729 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1278959689981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 6696123936 + ... + 6696124126.

It is an arithmetic number, because the mean of its divisors is an integer number (88566855311).

Almost surely, 2^{1278959689921} is an apocalyptic number.

1278959689921 is the 1130911-st square number.

1278959689921 is the 565456-th centered octagonal number.

It is an amenable number.

1278959689921 is a deficient number, since it is larger than the sum of its proper divisors (49543139744).

1278959689921 is an frugal number, since it uses more digits than its factorization.

1278959689921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 826 (or 222 counting only the distinct ones).

The product of its digits is 352719360, while the sum is 76.

The spelling of 1278959689921 in words is "one trillion, two hundred seventy-eight billion, nine hundred fifty-nine million, six hundred eighty-nine thousand, nine hundred twenty-one".