18439661 has 4 divisors (see below), whose sum is σ = 18492252. Its totient is φ = 18387072.

The previous prime is 18439657. The next prime is 18439669. The reversal of 18439661 is 16693481.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16693481 = 7 ⋅2384783.

It can be written as a sum of positive squares in 2 ways, for example, as 7344100 + 11095561 = 2710^2 + 3331^2 .

It is a cyclic number.

It is not a de Polignac number, because 18439661 - 2² = 18439657 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18439669) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25766 + ... + 26471.

It is an arithmetic number, because the mean of its divisors is an integer number (4623063).

Almost surely, 2^18439661 is an apocalyptic number.

It is an amenable number.

18439661 is a deficient number, since it is larger than the sum of its proper divisors (52591).

18439661 is an equidigital number, since it uses as much as digits as its factorization.

18439661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52590.

The product of its digits is 31104, while the sum is 38.

The square root of 18439661 is about 4294.1426385252. The cubic root of 18439661 is about 264.1907721581.

The spelling of 18439661 in words is "eighteen million, four hundred thirty-nine thousand, six hundred sixty-one".