18331661 has 4 divisors (see below), whose sum is σ = 19410012. Its totient is φ = 17253312.

The previous prime is 18331657. The next prime is 18331697. The reversal of 18331661 is 16613381.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16613381 = 2803 ⋅5927.

It can be written as a sum of positive squares in 2 ways, for example, as 11095561 + 7236100 = 3331^2 + 2690^2 .

It is a cyclic number.

It is not a de Polignac number, because 18331661 - 2² = 18331657 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 (18331361) 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, 539150 + ... + 539183.

It is an arithmetic number, because the mean of its divisors is an integer number (4852503).

Almost surely, 2^18331661 is an apocalyptic number.

It is an amenable number.

18331661 is a deficient number, since it is larger than the sum of its proper divisors (1078351).

18331661 is a wasteful number, since it uses less digits than its factorization.

18331661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1078350.

The product of its digits is 2592, while the sum is 29.

The square root of 18331661 is about 4281.5489019746. The cubic root of 18331661 is about 263.6739786743.

The spelling of 18331661 in words is "eighteen million, three hundred thirty-one thousand, six hundred sixty-one".