20716721 has 8 divisors (see below), whose sum is σ = 21669120. Its totient is φ = 19768672.

The previous prime is 20716697. The next prime is 20716739. The reversal of 20716721 is 12761702.

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 20716721 - 2¹⁰ = 20715697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20716741) 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, 12296 + ... + 13878.

It is an arithmetic number, because the mean of its divisors is an integer number (2708640).

Almost surely, 2^20716721 is an apocalyptic number.

It is an amenable number.

20716721 is a deficient number, since it is larger than the sum of its proper divisors (952399).

20716721 is a wasteful number, since it uses less digits than its factorization.

20716721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2175.

The product of its (nonzero) digits is 1176, while the sum is 26.

The square root of 20716721 is about 4551.5624789736. The cubic root of 20716721 is about 274.6462492743.

The spelling of 20716721 in words is "twenty million, seven hundred sixteen thousand, seven hundred twenty-one".