21308310 has 96 divisors (see below), whose sum is σ = 61832160. Its totient is φ = 5059584.

The previous prime is 21308303. The next prime is 21308311. The reversal of 21308310 is 1380312.

21308310 = T₄₉₃ + T₄₉₄ + ... + T₆₂₇.

It is a super-2 number, since 2×21308310² = 908088150112200, which contains 22 as substring.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21308311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 28704 + ... + 29436.

It is an arithmetic number, because the mean of its divisors is an integer number (644085).

Almost surely, 2^21308310 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21308310, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30916080).

21308310 is an abundant number, since it is smaller than the sum of its proper divisors (40523850).

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

21308310 is a wasteful number, since it uses less digits than its factorization.

21308310 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 782 (or 779 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 21308310 is about 4616.0925034059. The cubic root of 21308310 is about 277.2360284999.

Adding to 21308310 its reverse (1380312), we get a palindrome (22688622).

It can be divided in two parts, 2130 and 8310, that added together give a triangular number (10440 = T₁₄₄).

The spelling of 21308310 in words is "twenty-one million, three hundred eight thousand, three hundred ten".