918209821 has 2 divisors, whose sum is σ = 918209822. Its totient is φ = 918209820.

The previous prime is 918209791. The next prime is 918209869. The reversal of 918209821 is 128902819.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 654796921 + 263412900 = 25589^2 + 16230^2 .

It is a cyclic number.

It is not a de Polignac number, because 918209821 - 2¹⁵ = 918177053 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (918209891) 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 as a sum of consecutive naturals, namely, 459104910 + 459104911.

It is an arithmetic number, because the mean of its divisors is an integer number (459104911).

Almost surely, 2^918209821 is an apocalyptic number.

It is an amenable number.

918209821 is a deficient number, since it is larger than the sum of its proper divisors (1).

918209821 is an equidigital number, since it uses as much as digits as its factorization.

918209821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20736, while the sum is 40.

The square root of 918209821 is about 30301.9771797155. The cubic root of 918209821 is about 971.9575803404.

The spelling of 918209821 in words is "nine hundred eighteen million, two hundred nine thousand, eight hundred twenty-one".