918417721 has 4 divisors (see below), whose sum is σ = 989065252. Its totient is φ = 847770192.

The previous prime is 918417697. The next prime is 918417757. The reversal of 918417721 is 127714819.

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 102515625 + 815902096 = 10125^2 + 28564^2 .

It is a cyclic number.

It is not a de Polignac number, because 918417721 - 2⁷ = 918417593 is a prime.

It is a super-2 number, since 2×918417721² = 1686982220493667682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (918417781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 35323746 + ... + 35323771.

It is an arithmetic number, because the mean of its divisors is an integer number (247266313).

Almost surely, 2^918417721 is an apocalyptic number.

It is an amenable number.

918417721 is a deficient number, since it is larger than the sum of its proper divisors (70647531).

918417721 is a wasteful number, since it uses less digits than its factorization.

918417721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70647530.

The product of its digits is 28224, while the sum is 40.

The square root of 918417721 is about 30305.4074547761. The cubic root of 918417721 is about 972.0309313064.

The spelling of 918417721 in words is "nine hundred eighteen million, four hundred seventeen thousand, seven hundred twenty-one".