1278021601 has 2 divisors, whose sum is σ = 1278021602. Its totient is φ = 1278021600.

The previous prime is 1278021599. The next prime is 1278021617. The reversal of 1278021601 is 1061208721.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 941262400 + 336759201 = 30680^2 + 18351^2 .

It is a cyclic number.

It is not a de Polignac number, because 1278021601 - 2¹ = 1278021599 is a prime.

Together with 1278021599, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 1278021601.

It is not a weakly prime, because it can be changed into another prime (1278021671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 639010800 + 639010801.

It is an arithmetic number, because the mean of its divisors is an integer number (639010801).

Almost surely, 2^1278021601 is an apocalyptic number.

It is an amenable number.

1278021601 is a deficient number, since it is larger than the sum of its proper divisors (1).

1278021601 is an equidigital number, since it uses as much as digits as its factorization.

1278021601 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1344, while the sum is 28.

The square root of 1278021601 is about 35749.4279814377. The cubic root of 1278021601 is about 1085.2073622372.

The spelling of 1278021601 in words is "one billion, two hundred seventy-eight million, twenty-one thousand, six hundred one".