21305106 has 40 divisors (see below), whose sum is σ = 48003120. Its totient is φ = 7062552.

The previous prime is 21305101. The next prime is 21305113. The reversal of 21305106 is 60150312.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21305101) 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, 56025 + ... + 56403.

It is an arithmetic number, because the mean of its divisors is an integer number (1200078).

Almost surely, 2^21305106 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21305106, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24001560).

21305106 is an abundant number, since it is smaller than the sum of its proper divisors (26698014).

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

21305106 is a wasteful number, since it uses less digits than its factorization.

21305106 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 740 (or 731 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 21305106 is about 4615.7454435876. The cubic root of 21305106 is about 277.2221323758. Note that the first 3 decimals are identical.

Adding to 21305106 its reverse (60150312), we get a palindrome (81455418).

The spelling of 21305106 in words is "twenty-one million, three hundred five thousand, one hundred six".