21218450818 has 4 divisors (see below), whose sum is σ = 31827676230. Its totient is φ = 10609225408.

The previous prime is 21218450807. The next prime is 21218450833. The reversal of 21218450818 is 81805481212.

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., 18750646489 + 2467804329 = 136933^2 + 49677^2 .

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5304612703 + ... + 5304612706.

Almost surely, 2^21218450818 is an apocalyptic number.

21218450818 is a deficient number, since it is larger than the sum of its proper divisors (10609225412).

21218450818 is a wasteful number, since it uses less digits than its factorization.

21218450818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10609225411.

The product of its (nonzero) digits is 40960, while the sum is 40.

The spelling of 21218450818 in words is "twenty-one billion, two hundred eighteen million, four hundred fifty thousand, eight hundred eighteen".