1255778021 has 2 divisors, whose sum is σ = 1255778022. Its totient is φ = 1255778020.

The previous prime is 1255778011. The next prime is 1255778033. The reversal of 1255778021 is 1208775521.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1231027396 + 24750625 = 35086^2 + 4975^2 .

It is an emirp because it is prime and its reverse (1208775521) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1255778021 - 2¹⁰ = 1255776997 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1255778011) 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 as a sum of consecutive naturals, namely, 627889010 + 627889011.

It is an arithmetic number, because the mean of its divisors is an integer number (627889011).

Almost surely, 2^1255778021 is an apocalyptic number.

It is an amenable number.

1255778021 is a deficient number, since it is larger than the sum of its proper divisors (1).

1255778021 is an equidigital number, since it uses as much as digits as its factorization.

1255778021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 39200, while the sum is 38.

The square root of 1255778021 is about 35436.9584050324. The cubic root of 1255778021 is about 1078.8745766786.

The spelling of 1255778021 in words is "one billion, two hundred fifty-five million, seven hundred seventy-eight thousand, twenty-one".