2181836381 has 4 divisors (see below), whose sum is σ = 2197762332. Its totient is φ = 2165910432.

The previous prime is 2181836369. The next prime is 2181836407. The reversal of 2181836381 is 1836381812.

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 744744100 + 1437092281 = 27290^2 + 37909^2 .

It is a cyclic number.

It is not a de Polignac number, because 2181836381 - 2⁶ = 2181836317 is a prime.

It is a super-2 number, since 2×2181836381² = 9520819986910354322, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2181836341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7962770 + ... + 7963043.

It is an arithmetic number, because the mean of its divisors is an integer number (549440583).

Almost surely, 2^2181836381 is an apocalyptic number.

It is an amenable number.

2181836381 is a deficient number, since it is larger than the sum of its proper divisors (15925951).

2181836381 is a wasteful number, since it uses less digits than its factorization.

2181836381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15925950.

The product of its digits is 55296, while the sum is 41.

The square root of 2181836381 is about 46710.1314598878. The cubic root of 2181836381 is about 1297.0022407007.

The spelling of 2181836381 in words is "two billion, one hundred eighty-one million, eight hundred thirty-six thousand, three hundred eighty-one".