1781340391 has 4 divisors (see below), whose sum is σ = 1789119400. Its totient is φ = 1773561384.

The previous prime is 1781340377. The next prime is 1781340433. The reversal of 1781340391 is 1930431871.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1781340391 - 2¹⁵ = 1781307623 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1781340391.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1781343391) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3889161 + ... + 3889618.

It is an arithmetic number, because the mean of its divisors is an integer number (447279850).

Almost surely, 2^1781340391 is an apocalyptic number.

1781340391 is a deficient number, since it is larger than the sum of its proper divisors (7779009).

1781340391 is an equidigital number, since it uses as much as digits as its factorization.

1781340391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7779008.

The product of its (nonzero) digits is 18144, while the sum is 37.

The square root of 1781340391 is about 42205.9283868984. The cubic root of 1781340391 is about 1212.2224008414. Note that the first 3 decimals are identical.

The spelling of 1781340391 in words is "one billion, seven hundred eighty-one million, three hundred forty thousand, three hundred ninety-one".