21798418 has 4 divisors (see below), whose sum is σ = 32697630. Its totient is φ = 10899208.

The previous prime is 21798409. The next prime is 21798419. The reversal of 21798418 is 81489712.

It is a happy number.

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., 16024009 + 5774409 = 4003^2 + 2403^2 .

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 (21798419) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5449603 + ... + 5449606.

Almost surely, 2^21798418 is an apocalyptic number.

21798418 is a deficient number, since it is larger than the sum of its proper divisors (10899212).

21798418 is a wasteful number, since it uses less digits than its factorization.

21798418 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10899211.

The product of its digits is 32256, while the sum is 40.

The square root of 21798418 is about 4668.8775953113. The cubic root of 21798418 is about 279.3454865416.

The spelling of 21798418 in words is "twenty-one million, seven hundred ninety-eight thousand, four hundred eighteen".