21108436 has 6 divisors (see below), whose sum is σ = 36939770. Its totient is φ = 10554216.

The previous prime is 21108431. The next prime is 21108497. The reversal of 21108436 is 63480112.

It can be written as a sum of positive squares in only one way, i.e., 21104836 + 3600 = 4594^2 + 60^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21108436.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21108431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2638551 + ... + 2638558.

Almost surely, 2^21108436 is an apocalyptic number.

It is an amenable number.

21108436 is a deficient number, since it is larger than the sum of its proper divisors (15831334).

21108436 is a wasteful number, since it uses less digits than its factorization.

21108436 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5277113 (or 5277111 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 21108436 is about 4594.3917987042. The cubic root of 21108436 is about 276.3664704103.

Adding to 21108436 its reverse (63480112), we get a palindrome (84588548).

The spelling of 21108436 in words is "twenty-one million, one hundred eight thousand, four hundred thirty-six".