218145021 has 4 divisors (see below), whose sum is σ = 290860032. Its totient is φ = 145430012.

The previous prime is 218145017. The next prime is 218145029. The reversal of 218145021 is 120541812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 218145021 - 2² = 218145017 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 218144982 and 218145000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (218145029) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 36357501 + ... + 36357506.

It is an arithmetic number, because the mean of its divisors is an integer number (72715008).

Almost surely, 2^218145021 is an apocalyptic number.

It is an amenable number.

218145021 is a deficient number, since it is larger than the sum of its proper divisors (72715011).

218145021 is an equidigital number, since it uses as much as digits as its factorization.

218145021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72715010.

The product of its (nonzero) digits is 640, while the sum is 24.

The square root of 218145021 is about 14769.7332745043. The cubic root of 218145021 is about 601.9795920647.

Adding to 218145021 its reverse (120541812), we get a palindrome (338686833).

The spelling of 218145021 in words is "two hundred eighteen million, one hundred forty-five thousand, twenty-one".