20650721 has 16 divisors (see below), whose sum is σ = 25544064. Its totient is φ = 16257024.

The previous prime is 20650691. The next prime is 20650753. The reversal of 20650721 is 12705602.

It is not a de Polignac number, because 20650721 - 2⁶ = 20650657 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20650771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22946 + ... + 23828.

It is an arithmetic number, because the mean of its divisors is an integer number (1596504).

Almost surely, 2^20650721 is an apocalyptic number.

It is an amenable number.

20650721 is a deficient number, since it is larger than the sum of its proper divisors (4893343).

20650721 is a wasteful number, since it uses less digits than its factorization.

20650721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1160.

The product of its (nonzero) digits is 840, while the sum is 23.

The square root of 20650721 is about 4544.3064377306. The cubic root of 20650721 is about 274.3542800307.

The spelling of 20650721 in words is "twenty million, six hundred fifty thousand, seven hundred twenty-one".