20113721 has 2 divisors, whose sum is σ = 20113722. Its totient is φ = 20113720.

The previous prime is 20113673. The next prime is 20113747. The reversal of 20113721 is 12731102.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10725625 + 9388096 = 3275^2 + 3064^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20113721 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 20113721.

It is not a weakly prime, because it can be changed into another prime (20113421) 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 as a sum of consecutive naturals, namely, 10056860 + 10056861.

It is an arithmetic number, because the mean of its divisors is an integer number (10056861).

Almost surely, 2^20113721 is an apocalyptic number.

It is an amenable number.

20113721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20113721 is an equidigital number, since it uses as much as digits as its factorization.

20113721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 84, while the sum is 17.

The square root of 20113721 is about 4484.8323268546. The cubic root of 20113721 is about 271.9552667569.

Adding to 20113721 its reverse (12731102), we get a palindrome (32844823).

The spelling of 20113721 in words is "twenty million, one hundred thirteen thousand, seven hundred twenty-one".