21299818 has 4 divisors (see below), whose sum is σ = 31949730. Its totient is φ = 10649908.

The previous prime is 21299813. The next prime is 21299843. The reversal of 21299818 is 81899212.

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., 20638849 + 660969 = 4543^2 + 813^2 .

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 not an unprimeable number, because it can be changed into a prime (21299813) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5324953 + ... + 5324956.

Almost surely, 2^21299818 is an apocalyptic number.

21299818 is a deficient number, since it is larger than the sum of its proper divisors (10649912).

21299818 is a wasteful number, since it uses less digits than its factorization.

21299818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10649911.

The product of its digits is 20736, while the sum is 40.

The square root of 21299818 is about 4615.1725861554. The cubic root of 21299818 is about 277.1991946515.

The spelling of 21299818 in words is "twenty-one million, two hundred ninety-nine thousand, eight hundred eighteen".