218976921 has 6 divisors (see below), whose sum is σ = 316300010. Its totient is φ = 145984608.

The previous prime is 218976911. The next prime is 218976929. The reversal of 218976921 is 129679812.

It can be written as a sum of positive squares in only one way, i.e., 115670025 + 103306896 = 10755^2 + 10164^2 .

It is a de Polignac number, because none of the positive numbers 2^k-218976921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (218976929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 12165376 + ... + 12165393.

Almost surely, 2^218976921 is an apocalyptic number.

It is an amenable number.

218976921 is a deficient number, since it is larger than the sum of its proper divisors (97323089).

218976921 is a wasteful number, since it uses less digits than its factorization.

218976921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24330775 (or 24330772 counting only the distinct ones).

The product of its digits is 108864, while the sum is 45.

The square root of 218976921 is about 14797.8687992562. The cubic root of 218976921 is about 602.7438414297.

The spelling of 218976921 in words is "two hundred eighteen million, nine hundred seventy-six thousand, nine hundred twenty-one".