20201021 has 2 divisors, whose sum is σ = 20201022. Its totient is φ = 20201020.

The previous prime is 20200993. The next prime is 20201029. The reversal of 20201021 is 12010202.

It is an a-pointer prime, because the next prime (20201029) can be obtained adding 20201021 to its sum of digits (8).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18156121 + 2044900 = 4261^2 + 1430^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20201021 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20201029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10100510 + 10100511.

It is an arithmetic number, because the mean of its divisors is an integer number (10100511).

Almost surely, 2^20201021 is an apocalyptic number.

It is an amenable number.

20201021 is a deficient number, since it is larger than the sum of its proper divisors (1).

20201021 is an equidigital number, since it uses as much as digits as its factorization.

20201021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8, while the sum is 8.

The square root of 20201021 is about 4494.5545941728. The cubic root of 20201021 is about 272.3481565744.

Adding to 20201021 its reverse (12010202), we get a palindrome (32211223).

The spelling of 20201021 in words is "twenty million, two hundred one thousand, twenty-one".