21064720 has 40 divisors (see below), whose sum is σ = 49282560. Its totient is φ = 8373120.

The previous prime is 21064679. The next prime is 21064723. The reversal of 21064720 is 2746012.

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 21064691 and 21064700.

It is not an unprimeable number, because it can be changed into a prime (21064723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13585 + ... + 15055.

It is an arithmetic number, because the mean of its divisors is an integer number (1232064).

Almost surely, 2^21064720 is an apocalyptic number.

21064720 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 21064720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24641280).

21064720 is an abundant number, since it is smaller than the sum of its proper divisors (28217840).

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

21064720 is a wasteful number, since it uses less digits than its factorization.

21064720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1663 (or 1657 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 22.

The square root of 21064720 is about 4589.6317935102. The cubic root of 21064720 is about 276.1755516915.

The spelling of 21064720 in words is "twenty-one million, sixty-four thousand, seven hundred twenty".