21123120 has 80 divisors (see below), whose sum is σ = 65924352. Its totient is φ = 5594880.

The previous prime is 21123119. The next prime is 21123133. The reversal of 21123120 is 2132112.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 21123096 and 21123105.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 67765 + ... + 68075.

Almost surely, 2^21123120 is an apocalyptic number.

21123120 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 21123120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32962176).

21123120 is an abundant number, since it is smaller than the sum of its proper divisors (44801232).

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

21123120 is a wasteful number, since it uses less digits than its factorization.

21123120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 610 (or 604 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 21123120 is about 4595.9895561239. The cubic root of 21123120 is about 276.4305399699.

Adding to 21123120 its reverse (2132112), we get a palindrome (23255232).

The spelling of 21123120 in words is "twenty-one million, one hundred twenty-three thousand, one hundred twenty".