20145821 has 2 divisors, whose sum is σ = 20145822. Its totient is φ = 20145820.

The previous prime is 20145809. The next prime is 20145847. The reversal of 20145821 is 12854102.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19456921 + 688900 = 4411^2 + 830^2 .

It is a cyclic number.

It is not a de Polignac number, because 20145821 - 2¹⁰ = 20144797 is a prime.

It is a Chen prime.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20145421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10072910 + 10072911.

It is an arithmetic number, because the mean of its divisors is an integer number (10072911).

Almost surely, 2^20145821 is an apocalyptic number.

It is an amenable number.

20145821 is a deficient number, since it is larger than the sum of its proper divisors (1).

20145821 is an equidigital number, since it uses as much as digits as its factorization.

20145821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 20145821 is about 4488.4096292562. The cubic root of 20145821 is about 272.0998633096.

Adding to 20145821 its reverse (12854102), we get a palindrome (32999923).

The spelling of 20145821 in words is "twenty million, one hundred forty-five thousand, eight hundred twenty-one".