1780561978129 has 81 divisors (see below), whose sum is σ = 2094537242161. Its totient is φ = 1512436266880.

The previous prime is 1780561978109. The next prime is 1780561978201. The reversal of 1780561978129 is 9218791650871.

The square root of 1780561978129 is 1334377.

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

It can be written as a sum of positive squares in 4 ways, for example, as 163035865729 + 1617526112400 = 403777^2 + 1271820^2 .

It is not a de Polignac number, because 1780561978129 - 2⁹ = 1780561977617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1780561978109) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 20006314317 + ... + 20006314405.

Almost surely, 2^{1780561978129} is an apocalyptic number.

1780561978129 is the 1334377-th square number.

1780561978129 is the 667189-th centered octagonal number.

It is an amenable number.

1780561978129 is a deficient number, since it is larger than the sum of its proper divisors (313975264032).

1780561978129 is an frugal number, since it uses more digits than its factorization.

1780561978129 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 352 (or 176 counting only the distinct ones).

The product of its (nonzero) digits is 15240960, while the sum is 64.

Multiplying 1780561978129 by its sum of digits (64), we get a square (113955966600256 = 10675016²).

The spelling of 1780561978129 in words is "one trillion, seven hundred eighty billion, five hundred sixty-one million, nine hundred seventy-eight thousand, one hundred twenty-nine".