918181921 has 8 divisors (see below), whose sum is σ = 950277384. Its totient is φ = 886548480.

The previous prime is 918181907. The next prime is 918181931. The reversal of 918181921 is 129181819.

It can be written as a sum of positive squares in 4 ways, for example, as 15840400 + 902341521 = 3980^2 + 30039^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 918181921 - 2⁷ = 918181793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (918181931) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 111460 + ... + 119413.

It is an arithmetic number, because the mean of its divisors is an integer number (118784673).

Almost surely, 2^918181921 is an apocalyptic number.

It is an amenable number.

918181921 is a deficient number, since it is larger than the sum of its proper divisors (32095463).

918181921 is a wasteful number, since it uses less digits than its factorization.

918181921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 231011.

The product of its digits is 10368, while the sum is 40.

The square root of 918181921 is about 30301.5168102193. The cubic root of 918181921 is about 971.9477358617.

It can be divided in two parts, 91818 and 1921, that added together give a palindrome (93739).

The spelling of 918181921 in words is "nine hundred eighteen million, one hundred eighty-one thousand, nine hundred twenty-one".