18913661 has 4 divisors (see below), whose sum is σ = 20368572. Its totient is φ = 17458752.

The previous prime is 18913637. The next prime is 18913663. The reversal of 18913661 is 16631981.

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 4813636 + 14100025 = 2194^2 + 3755^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18913661 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 (18913663) 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, 727436 + ... + 727461.

It is an arithmetic number, because the mean of its divisors is an integer number (5092143).

Almost surely, 2^18913661 is an apocalyptic number.

It is an amenable number.

18913661 is a deficient number, since it is larger than the sum of its proper divisors (1454911).

18913661 is a wasteful number, since it uses less digits than its factorization.

18913661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1454910.

The product of its digits is 7776, while the sum is 35.

The square root of 18913661 is about 4348.9839043160. The cubic root of 18913661 is about 266.4353631433.

The spelling of 18913661 in words is "eighteen million, nine hundred thirteen thousand, six hundred sixty-one".