20682721 has 8 divisors (see below), whose sum is σ = 21098600. Its totient is φ = 20269440.

The previous prime is 20682719. The next prime is 20682743. The reversal of 20682721 is 12728602.

It can be written as a sum of positive squares in 4 ways, for example, as 2739025 + 17943696 = 1655^2 + 4236^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20682721 - 2¹ = 20682719 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20682721.

It is not an unprimeable number, because it can be changed into a prime (20682751) 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, 24535 + ... + 25363.

It is an arithmetic number, because the mean of its divisors is an integer number (2637325).

Almost surely, 2^20682721 is an apocalyptic number.

It is an amenable number.

20682721 is a deficient number, since it is larger than the sum of its proper divisors (415879).

20682721 is an equidigital number, since it uses as much as digits as its factorization.

20682721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1299.

The product of its (nonzero) digits is 2688, while the sum is 28.

The square root of 20682721 is about 4547.8259641284. The cubic root of 20682721 is about 274.4959184443.

The spelling of 20682721 in words is "twenty million, six hundred eighty-two thousand, seven hundred twenty-one".