2181856493 has 4 divisors (see below), whose sum is σ = 2185198428. Its totient is φ = 2178514560.

The previous prime is 2181856487. The next prime is 2181856529. The reversal of 2181856493 is 3946581812.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 542983204 + 1638873289 = 23302^2 + 40483^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2181856493 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 (2181856423) 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, 1669988 + ... + 1671293.

It is an arithmetic number, because the mean of its divisors is an integer number (546299607).

Almost surely, 2^2181856493 is an apocalyptic number.

It is an amenable number.

2181856493 is a deficient number, since it is larger than the sum of its proper divisors (3341935).

2181856493 is an equidigital number, since it uses as much as digits as its factorization.

2181856493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3341934.

The product of its digits is 414720, while the sum is 47.

The square root of 2181856493 is about 46710.3467445918. The cubic root of 2181856493 is about 1297.0062259107.

The spelling of 2181856493 in words is "two billion, one hundred eighty-one million, eight hundred fifty-six thousand, four hundred ninety-three".