21816806 has 16 divisors (see below), whose sum is σ = 35803728. Its totient is φ = 9888000.

The previous prime is 21816803. The next prime is 21816841. The reversal of 21816806 is 60861812.

It is a super-3 number, since 3×21816806³ (a number of 23 digits) contains 333 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21816803) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7586 + ... + 10058.

It is an arithmetic number, because the mean of its divisors is an integer number (2237733).

Almost surely, 2^21816806 is an apocalyptic number.

21816806 is a deficient number, since it is larger than the sum of its proper divisors (13986922).

21816806 is a wasteful number, since it uses less digits than its factorization.

21816806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2887.

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 21816806 is about 4670.8463901096. The cubic root of 21816806 is about 279.4240115238.

It can be divided in two parts, 21816 and 806, that added together give a palindrome (22622).

The spelling of 21816806 in words is "twenty-one million, eight hundred sixteen thousand, eight hundred six".