218724561 has 72 divisors (see below), whose sum is σ = 377975520. Its totient is φ = 121532400.

The previous prime is 218724553. The next prime is 218724577. The reversal of 218724561 is 165427812.

218724561 is a `hidden beast` number, since 21 + 8 + 72 + 4 + 561 = 666.

It is not a de Polignac number, because 218724561 - 2³ = 218724553 is a prime.

Its product of digits (26880) is a multiple of the sum of its prime divisors (64).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (218724581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 7055616 + ... + 7055646.

It is an arithmetic number, because the mean of its divisors is an integer number (5249660).

Almost surely, 2^218724561 is an apocalyptic number.

It is an amenable number.

218724561 is a deficient number, since it is larger than the sum of its proper divisors (159250959).

218724561 is a wasteful number, since it uses less digits than its factorization.

218724561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 120 (or 64 counting only the distinct ones).

The product of its digits is 26880, while the sum is 36.

The square root of 218724561 is about 14789.3394375814. The cubic root of 218724561 is about 602.5122083349.

The spelling of 218724561 in words is "two hundred eighteen million, seven hundred twenty-four thousand, five hundred sixty-one".