21007120 has 80 divisors (see below), whose sum is σ = 51568128. Its totient is φ = 7948800.

The previous prime is 21007111. The next prime is 21007123. The reversal of 21007120 is 2170012.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21007120.

It is not an unprimeable number, because it can be changed into a prime (21007123) by changing a digit.

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, 139045 + ... + 139195.

Almost surely, 2^21007120 is an apocalyptic number.

21007120 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 21007120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25784064).

21007120 is an abundant number, since it is smaller than the sum of its proper divisors (30561008).

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

21007120 is a wasteful number, since it uses less digits than its factorization.

21007120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 248 (or 242 counting only the distinct ones).

The product of its (nonzero) digits is 28, while the sum is 13.

The square root of 21007120 is about 4583.3524848085. The cubic root of 21007120 is about 275.9235943374.

Adding to 21007120 its reverse (2170012), we get a palindrome (23177132).

The spelling of 21007120 in words is "twenty-one million, seven thousand, one hundred twenty".