20721400 has 144 divisors (see below), whose sum is σ = 59527440. Its totient is φ = 6566400.

The previous prime is 20721397. The next prime is 20721401. The reversal of 20721400 is 412702.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20721401) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 505380 + ... + 505420.

It is an arithmetic number, because the mean of its divisors is an integer number (413385).

Almost surely, 2^20721400 is an apocalyptic number.

20721400 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 20721400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29763720).

20721400 is an abundant number, since it is smaller than the sum of its proper divisors (38806040).

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

20721400 is a wasteful number, since it uses less digits than its factorization.

20721400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 102 (or 74 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 16.

The square root of 20721400 is about 4552.0764492702. The cubic root of 20721400 is about 274.6669245711. Note that the first 3 decimals are identical.

The spelling of 20721400 in words is "twenty million, seven hundred twenty-one thousand, four hundred".