20501905 has 4 divisors (see below), whose sum is σ = 24602292. Its totient is φ = 16401520.

The previous prime is 20501879. The next prime is 20501909. The reversal of 20501905 is 50910502.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11881809 + 8620096 = 3447^2 + 2936^2 .

It is not a de Polignac number, because 20501905 - 2²¹ = 18404753 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20501909) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2050186 + ... + 2050195.

It is an arithmetic number, because the mean of its divisors is an integer number (6150573).

Almost surely, 2^20501905 is an apocalyptic number.

It is an amenable number.

20501905 is a deficient number, since it is larger than the sum of its proper divisors (4100387).

20501905 is an equidigital number, since it uses as much as digits as its factorization.

20501905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4100386.

The product of its (nonzero) digits is 450, while the sum is 22.

The square root of 20501905 is about 4527.9029362388. The cubic root of 20501905 is about 273.6936610428.

The spelling of 20501905 in words is "twenty million, five hundred one thousand, nine hundred five".