1780378500821 has 2 divisors, whose sum is σ = 1780378500822. Its totient is φ = 1780378500820.

The previous prime is 1780378500749. The next prime is 1780378500827. The reversal of 1780378500821 is 1280058730871.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1299178234225 + 481200266596 = 1139815^2 + 693686^2 .

It is an emirp because it is prime and its reverse (1280058730871) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1780378500821 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1780378500821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1780378500827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 890189250410 + 890189250411.

It is an arithmetic number, because the mean of its divisors is an integer number (890189250411).

Almost surely, 2^{1780378500821} is an apocalyptic number.

It is an amenable number.

1780378500821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1780378500821 is an equidigital number, since it uses as much as digits as its factorization.

1780378500821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 752640, while the sum is 50.

The spelling of 1780378500821 in words is "one trillion, seven hundred eighty billion, three hundred seventy-eight million, five hundred thousand, eight hundred twenty-one".