21000918 has 16 divisors (see below), whose sum is σ = 42255360. Its totient is φ = 6958056.

The previous prime is 21000913. The next prime is 21000953. The reversal of 21000918 is 81900012.

It is a junction number, because it is equal to n+sod(n) for n = 21000894 and 21000903.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000911) 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 in 7 ways as a sum of consecutive naturals, for example, 9478 + ... + 11481.

It is an arithmetic number, because the mean of its divisors is an integer number (2640960).

Almost surely, 2^21000918 is an apocalyptic number.

21000918 is an abundant number, since it is smaller than the sum of its proper divisors (21254442).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21000918 is a wasteful number, since it uses less digits than its factorization.

21000918 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21131.

The product of its (nonzero) digits is 144, while the sum is 21.

The square root of 21000918 is about 4582.6758558729. The cubic root of 21000918 is about 275.8964377262.

The spelling of 21000918 in words is "twenty-one million, nine hundred eighteen", and thus it is an aban number.