18215561 has 8 divisors (see below), whose sum is σ = 22419264. Its totient is φ = 14412240.

The previous prime is 18215557. The next prime is 18215579. The reversal of 18215561 is 16551281.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18215561 - 2² = 18215557 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18215501) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 99995 + ... + 100176.

It is an arithmetic number, because the mean of its divisors is an integer number (2802408).

Almost surely, 2^18215561 is an apocalyptic number.

It is an amenable number.

18215561 is a deficient number, since it is larger than the sum of its proper divisors (4203703).

18215561 is a wasteful number, since it uses less digits than its factorization.

18215561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 200191.

The product of its digits is 2400, while the sum is 29.

The square root of 18215561 is about 4267.9691892046. The cubic root of 18215561 is about 263.1161568184.

The spelling of 18215561 in words is "eighteen million, two hundred fifteen thousand, five hundred sixty-one".