1781234567641 has 3 divisors (see below), whose sum is σ = 1781235902271. Its totient is φ = 1781233233012.

The previous prime is 1781234567633. The next prime is 1781234567737. The reversal of 1781234567641 is 1467654321871.

The square root of 1781234567641 is 1334629.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 453439277641 + 1327795290000 = 673379^2 + 1152300^2 .

It is not a de Polignac number, because 1781234567641 - 2³ = 1781234567633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1781234567621) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 667315 + ... + 2001943.

It is an arithmetic number, because the mean of its divisors is an integer number (593745300757).

Almost surely, 2^{1781234567641} is an apocalyptic number.

1781234567641 is the 1334629-th square number.

1781234567641 is the 667315-th centered octagonal number.

It is an amenable number.

1781234567641 is a deficient number, since it is larger than the sum of its proper divisors (1334630).

1781234567641 is an frugal number, since it uses more digits than its factorization.

1781234567641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2669258 (or 1334629 counting only the distinct ones).

The product of its digits is 6773760, while the sum is 55.

The spelling of 1781234567641 in words is "one trillion, seven hundred eighty-one billion, two hundred thirty-four million, five hundred sixty-seven thousand, six hundred forty-one".