1378766561 has 2 divisors, whose sum is σ = 1378766562. Its totient is φ = 1378766560.

The previous prime is 1378766489. The next prime is 1378766567. The reversal of 1378766561 is 1656678731.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1329331600 + 49434961 = 36460^2 + 7031^2 .

It is an emirp because it is prime and its reverse (1656678731) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1378766561 - 2¹⁰ = 1378765537 is a prime.

It is not a weakly prime, because it can be changed into another prime (1378766567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 689383280 + 689383281.

It is an arithmetic number, because the mean of its divisors is an integer number (689383281).

Almost surely, 2^1378766561 is an apocalyptic number.

It is an amenable number.

1378766561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1378766561 is an equidigital number, since it uses as much as digits as its factorization.

1378766561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1270080, while the sum is 50.

The square root of 1378766561 is about 37131.7459998853. The cubic root of 1378766561 is about 1113.0044840033.

The spelling of 1378766561 in words is "one billion, three hundred seventy-eight million, seven hundred sixty-six thousand, five hundred sixty-one".