20218521 has 8 divisors (see below), whose sum is σ = 27034560. Its totient is φ = 13440752.

The previous prime is 20218477. The next prime is 20218529. The reversal of 20218521 is 12581202.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20218521 - 2¹⁷ = 20087449 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20218529) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8310 + ... + 10463.

It is an arithmetic number, because the mean of its divisors is an integer number (3379320).

Almost surely, 2^20218521 is an apocalyptic number.

It is an amenable number.

20218521 is a deficient number, since it is larger than the sum of its proper divisors (6816039).

20218521 is a wasteful number, since it uses less digits than its factorization.

20218521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19135.

The product of its (nonzero) digits is 320, while the sum is 21.

The square root of 20218521 is about 4496.5009729789. The cubic root of 20218521 is about 272.4267782956.

Adding to 20218521 its reverse (12581202), we get a palindrome (32799723).

The spelling of 20218521 in words is "twenty million, two hundred eighteen thousand, five hundred twenty-one".