18107821 has 8 divisors (see below), whose sum is σ = 18581400. Its totient is φ = 17639232.

The previous prime is 18107801. The next prime is 18107849. The reversal of 18107821 is 12870181.

It can be written as a sum of positive squares in 4 ways, for example, as 585225 + 17522596 = 765^2 + 4186^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18107821 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18107821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18107801) 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, 6751 + ... + 9043.

It is an arithmetic number, because the mean of its divisors is an integer number (2322675).

Almost surely, 2^18107821 is an apocalyptic number.

It is an amenable number.

18107821 is a deficient number, since it is larger than the sum of its proper divisors (473579).

18107821 is a wasteful number, since it uses less digits than its factorization.

18107821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2495.

The product of its (nonzero) digits is 896, while the sum is 28.

The square root of 18107821 is about 4255.3285419577. The cubic root of 18107821 is about 262.5963776111.

The spelling of 18107821 in words is "eighteen million, one hundred seven thousand, eight hundred twenty-one".