20721344 has 56 divisors (see below), whose sum is σ = 49060608. Its totient is φ = 8490240.

The previous prime is 20721329. The next prime is 20721353. The reversal of 20721344 is 44312702.

It is a tau number, because it is divible by the number of its divisors (56).

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9299 + ... + 11309.

Almost surely, 2^20721344 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20721344, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24530304).

20721344 is an abundant number, since it is smaller than the sum of its proper divisors (28339264).

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

20721344 is a wasteful number, since it uses less digits than its factorization.

20721344 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2053 (or 2043 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 23.

The square root of 20721344 is about 4552.0702982270. The cubic root of 20721344 is about 274.6666771400. Note that the first 4 decimals are identical.

The spelling of 20721344 in words is "twenty million, seven hundred twenty-one thousand, three hundred forty-four".