21808106 has 8 divisors (see below), whose sum is σ = 32734884. Its totient is φ = 10896480.

The previous prime is 21808103. The next prime is 21808109. The reversal of 21808106 is 60180812.

It is an interprime number because it is at equal distance from previous prime (21808103) and next prime (21808109).

It can be written as a sum of positive squares in 2 ways, for example, as 17986081 + 3822025 = 4241^2 + 1955^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21808103) 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, 1046 + ... + 6686.

Almost surely, 2^21808106 is an apocalyptic number.

21808106 is a deficient number, since it is larger than the sum of its proper divisors (10926778).

21808106 is a wasteful number, since it uses less digits than its factorization.

21808106 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7576.

The product of its (nonzero) digits is 768, while the sum is 26.

The square root of 21808106 is about 4669.9149885196. The cubic root of 21808106 is about 279.3868641352.

Adding to 21808106 its reverse (60180812), we get a palindrome (81988918).

The spelling of 21808106 in words is "twenty-one million, eight hundred eight thousand, one hundred six".