20288721 has 8 divisors (see below), whose sum is σ = 27086560. Its totient is φ = 13508352.

The previous prime is 20288717. The next prime is 20288731. The reversal of 20288721 is 12788202.

It is a happy number.

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

It is not a de Polignac number, because 20288721 - 2² = 20288717 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20288711) 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, 1360 + ... + 6513.

It is an arithmetic number, because the mean of its divisors is an integer number (3385820).

Almost surely, 2^20288721 is an apocalyptic number.

It is an amenable number.

20288721 is a deficient number, since it is larger than the sum of its proper divisors (6797839).

20288721 is an equidigital number, since it uses as much as digits as its factorization.

20288721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8735.

The product of its (nonzero) digits is 3584, while the sum is 30.

The square root of 20288721 is about 4504.3002786226. The cubic root of 20288721 is about 272.7417084985.

The spelling of 20288721 in words is "twenty million, two hundred eighty-eight thousand, seven hundred twenty-one".