18201561 has 16 divisors (see below), whose sum is σ = 27813888. Its totient is φ = 10371600.

The previous prime is 18201553. The next prime is 18201569. The reversal of 18201561 is 16510281.

18201561 is a nontrivial binomial coefficient, being equal to C(6034, 2).

It is an interprime number because it is at equal distance from previous prime (18201553) and next prime (18201569).

It is not a de Polignac number, because 18201561 - 2³ = 18201553 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18201569) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8046 + ... + 10056.

It is an arithmetic number, because the mean of its divisors is an integer number (1738368).

Almost surely, 2^18201561 is an apocalyptic number.

18201561 is the 6033-rd triangular number and also the 3017-th hexagonal number.

It is an amenable number.

18201561 is a deficient number, since it is larger than the sum of its proper divisors (9612327).

18201561 is a wasteful number, since it uses less digits than its factorization.

18201561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2452.

The product of its (nonzero) digits is 480, while the sum is 24.

The square root of 18201561 is about 4266.3287496394. The cubic root of 18201561 is about 263.0487314944.

The spelling of 18201561 in words is "eighteen million, two hundred one thousand, five hundred sixty-one".