1821231918 has 64 divisors (see below), whose sum is σ = 4434393600. Its totient is φ = 549478080.

The previous prime is 1821231911. The next prime is 1821231949. The reversal of 1821231918 is 8191321281.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1821231911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 131823 + ... + 144981.

It is an arithmetic number, because the mean of its divisors is an integer number (69287400).

Almost surely, 2^1821231918 is an apocalyptic number.

1821231918 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 1821231918, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2217196800).

1821231918 is an abundant number, since it is smaller than the sum of its proper divisors (2613161682).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1821231918 is a wasteful number, since it uses less digits than its factorization.

1821231918 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13414 (or 13408 counting only the distinct ones).

The product of its digits is 6912, while the sum is 36.

The square root of 1821231918 is about 42675.8938746454. The cubic root of 1821231918 is about 1221.2045609855.

It can be divided in two parts, 182123 and 1918, that added together give a square (184041 = 429²).

The spelling of 1821231918 in words is "one billion, eight hundred twenty-one million, two hundred thirty-one thousand, nine hundred eighteen".