20218645 has 4 divisors (see below), whose sum is σ = 24262380. Its totient is φ = 16174912.

The previous prime is 20218637. The next prime is 20218669. The reversal of 20218645 is 54681202.

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 8868484 + 11350161 = 2978^2 + 3369^2 .

It is a cyclic number.

It is not a de Polignac number, because 20218645 - 2³ = 20218637 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2021860 + ... + 2021869.

It is an arithmetic number, because the mean of its divisors is an integer number (6065595).

Almost surely, 2^20218645 is an apocalyptic number.

It is an amenable number.

20218645 is a deficient number, since it is larger than the sum of its proper divisors (4043735).

20218645 is an equidigital number, since it uses as much as digits as its factorization.

20218645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4043734.

The product of its (nonzero) digits is 3840, while the sum is 28.

The square root of 20218645 is about 4496.5147614569. The cubic root of 20218645 is about 272.4273352247.

Adding to 20218645 its reverse (54681202), we get a palindrome (74899847).

The spelling of 20218645 in words is "twenty million, two hundred eighteen thousand, six hundred forty-five".