21106818 has 40 divisors (see below), whose sum is σ = 47754828. Its totient is φ = 6967296.

The previous prime is 21106769. The next prime is 21106819. The reversal of 21106818 is 81860112.

It can be written as a sum of positive squares in 2 ways, for example, as 20493729 + 613089 = 4527^2 + 783^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 21106791 and 21106800.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21106819) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 17730 + ... + 18882.

Almost surely, 2^21106818 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21106818, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23877414).

21106818 is an abundant number, since it is smaller than the sum of its proper divisors (26648010).

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

21106818 is a wasteful number, since it uses less digits than its factorization.

21106818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1280 (or 1271 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 27.

The square root of 21106818 is about 4594.2157110871. The cubic root of 21106818 is about 276.3594088990.

The spelling of 21106818 in words is "twenty-one million, one hundred six thousand, eight hundred eighteen".