218250721 has 4 divisors (see below), whose sum is σ = 235039252. Its totient is φ = 201462192.

The previous prime is 218250713. The next prime is 218250763. The reversal of 218250721 is 127052812.

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 132503121 + 85747600 = 11511^2 + 9260^2 .

It is a cyclic number.

It is not a de Polignac number, because 218250721 - 2³ = 218250713 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 218250721.

It is not an unprimeable number, because it can be changed into a prime (218250821) 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 3 ways as a sum of consecutive naturals, for example, 8394246 + ... + 8394271.

It is an arithmetic number, because the mean of its divisors is an integer number (58759813).

Almost surely, 2^218250721 is an apocalyptic number.

It is an amenable number.

218250721 is a deficient number, since it is larger than the sum of its proper divisors (16788531).

218250721 is a wasteful number, since it uses less digits than its factorization.

218250721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16788530.

The product of its (nonzero) digits is 2240, while the sum is 28.

The square root of 218250721 is about 14773.3111048268. The cubic root of 218250721 is about 602.0768041065.

The spelling of 218250721 in words is "two hundred eighteen million, two hundred fifty thousand, seven hundred twenty-one".