21918436 has 12 divisors (see below), whose sum is σ = 39293100. Its totient is φ = 10691840.

The previous prime is 21918427. The next prime is 21918437. The reversal of 21918436 is 63481912.

It can be written as a sum of positive squares in 2 ways, for example, as 295936 + 21622500 = 544^2 + 4650^2 .

It is not an unprimeable number, because it can be changed into a prime (21918437) 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 3 ways as a sum of consecutive naturals, for example, 66661 + ... + 66988.

It is an arithmetic number, because the mean of its divisors is an integer number (3274425).

Almost surely, 2^21918436 is an apocalyptic number.

It is an amenable number.

21918436 is a deficient number, since it is larger than the sum of its proper divisors (17374664).

21918436 is a wasteful number, since it uses less digits than its factorization.

21918436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133694 (or 133692 counting only the distinct ones).

The product of its digits is 10368, while the sum is 34.

The square root of 21918436 is about 4681.7129343863. The cubic root of 21918436 is about 279.8572231263.

The spelling of 21918436 in words is "twenty-one million, nine hundred eighteen thousand, four hundred thirty-six".