21185018 has 4 divisors (see below), whose sum is σ = 31777530. Its totient is φ = 10592508.

The previous prime is 21185011. The next prime is 21185023. The reversal of 21185018 is 81058112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 15816529 + 5368489 = 3977^2 + 2317^2 .

It is not an unprimeable number, because it can be changed into a prime (21185011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5296253 + ... + 5296256.

Almost surely, 2^21185018 is an apocalyptic number.

21185018 is a deficient number, since it is larger than the sum of its proper divisors (10592512).

21185018 is a wasteful number, since it uses less digits than its factorization.

21185018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10592511.

The product of its (nonzero) digits is 640, while the sum is 26.

The square root of 21185018 is about 4602.7185445126. The cubic root of 21185018 is about 276.7002888124.

The spelling of 21185018 in words is "twenty-one million, one hundred eighty-five thousand, eighteen".