21309120 has 252 divisors, whose sum is σ = 85825584. Its totient is φ = 4838400.

The previous prime is 21309107. The next prime is 21309133. The reversal of 21309120 is 2190312.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21309107) and next prime (21309133).

It is a tau number, because it is divible by the number of its divisors (252).

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

It is a junction number, because it is equal to n+sod(n) for n = 21309093 and 21309102.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 141045 + ... + 141195.

Almost surely, 2^21309120 is an apocalyptic number.

21309120 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21309120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42912792).

21309120 is an abundant number, since it is smaller than the sum of its proper divisors (64516464).

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

21309120 is a wasteful number, since it uses less digits than its factorization.

21309120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 188 (or 168 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 18.

The square root of 21309120 is about 4616.1802391155. The cubic root of 21309120 is about 277.2395413443.

Adding to 21309120 its reverse (2190312), we get a palindrome (23499432).

The spelling of 21309120 in words is "twenty-one million, three hundred nine thousand, one hundred twenty".