21026720 has 96 divisors (see below), whose sum is σ = 58423680. Its totient is φ = 7050240.

The previous prime is 21026717. The next prime is 21026741. The reversal of 21026720 is 2762012.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21026692 and 21026701.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22421 + ... + 23339.

It is an arithmetic number, because the mean of its divisors is an integer number (608580).

Almost surely, 2^21026720 is an apocalyptic number.

21026720 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 21026720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29211840).

21026720 is an abundant number, since it is smaller than the sum of its proper divisors (37396960).

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

21026720 is a wasteful number, since it uses less digits than its factorization.

21026720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 958 (or 950 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 20.

The square root of 21026720 is about 4585.4901591869. The cubic root of 21026720 is about 276.0093814637.

Adding to 21026720 its reverse (2762012), we get a palindrome (23788732).

The spelling of 21026720 in words is "twenty-one million, twenty-six thousand, seven hundred twenty".