2781721823 has 4 divisors (see below), whose sum is σ = 2782556280. Its totient is φ = 2780887368.

The previous prime is 2781721799. The next prime is 2781721829. The reversal of 2781721823 is 3281271872.

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 2781721823 - 2⁶ = 2781721759 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2781721829) 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, 412208 + ... + 418901.

It is an arithmetic number, because the mean of its divisors is an integer number (695639070).

Almost surely, 2^2781721823 is an apocalyptic number.

2781721823 is a deficient number, since it is larger than the sum of its proper divisors (834457).

2781721823 is an equidigital number, since it uses as much as digits as its factorization.

2781721823 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 834456.

The product of its digits is 75264, while the sum is 41.

The square root of 2781721823 is about 52742.0308956718. The cubic root of 2781721823 is about 1406.3861015189.

The spelling of 2781721823 in words is "two billion, seven hundred eighty-one million, seven hundred twenty-one thousand, eight hundred twenty-three".