18988661 has 4 divisors (see below), whose sum is σ = 19034400. Its totient is φ = 18942924.

The previous prime is 18988637. The next prime is 18988663. The reversal of 18988661 is 16688981.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 16688981 = 947 ⋅17623.

It is a cyclic number.

It is not a de Polignac number, because 18988661 - 2⁶ = 18988597 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18988663) 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, 22241 + ... + 23078.

It is an arithmetic number, because the mean of its divisors is an integer number (4758600).

Almost surely, 2^18988661 is an apocalyptic number.

It is an amenable number.

18988661 is a deficient number, since it is larger than the sum of its proper divisors (45739).

18988661 is an equidigital number, since it uses as much as digits as its factorization.

18988661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45738.

The product of its digits is 165888, while the sum is 47.

The square root of 18988661 is about 4357.5980769227. The cubic root of 18988661 is about 266.7870718418.

The spelling of 18988661 in words is "eighteen million, nine hundred eighty-eight thousand, six hundred sixty-one".