21681108 has 60 divisors (see below), whose sum is σ = 57660372. Its totient is φ = 7102080.

The previous prime is 21681097. The next prime is 21681113. The reversal of 21681108 is 80118612.

It can be written as a sum of positive squares in 2 ways, for example, as 2862864 + 18818244 = 1692^2 + 4338^2 .

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

It is a congruent number.

It is an unprimeable number.

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 19 ways as a sum of consecutive naturals, for example, 19216 + ... + 20312.

Almost surely, 2^21681108 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21681108, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28830186).

21681108 is an abundant number, since it is smaller than the sum of its proper divisors (35979264).

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

21681108 is a wasteful number, since it uses less digits than its factorization.

21681108 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1174 (or 1163 counting only the distinct ones).

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

The square root of 21681108 is about 4656.2976708969. The cubic root of 21681108 is about 278.8434779360.

The spelling of 21681108 in words is "twenty-one million, six hundred eighty-one thousand, one hundred eight".