18511661 has 6 divisors (see below), whose sum is σ = 21534030. Its totient is φ = 15867096.

The previous prime is 18511639. The next prime is 18511667. The reversal of 18511661 is 16611581.

It can be written as a sum of positive squares in only one way, i.e., 15642025 + 2869636 = 3955^2 + 1694^2 .

It is not a de Polignac number, because 18511661 - 2¹⁴ = 18495277 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18511667) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 188846 + ... + 188943.

It is an arithmetic number, because the mean of its divisors is an integer number (3589005).

Almost surely, 2^18511661 is an apocalyptic number.

It is an amenable number.

18511661 is a deficient number, since it is larger than the sum of its proper divisors (3022369).

18511661 is an equidigital number, since it uses as much as digits as its factorization.

18511661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 377803 (or 377796 counting only the distinct ones).

The product of its digits is 1440, while the sum is 29.

The square root of 18511661 is about 4302.5179836928. The cubic root of 18511661 is about 264.5341810665.

The spelling of 18511661 in words is "eighteen million, five hundred eleven thousand, six hundred sixty-one".