20231021 has 4 divisors (see below), whose sum is σ = 20241312. Its totient is φ = 20220732.

The previous prime is 20231017. The next prime is 20231023. The reversal of 20231021 is 12013202.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12013202 = 2 ⋅6006601.

It is a cyclic number.

It is not a de Polignac number, because 20231021 - 2² = 20231017 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 20230993 and 20231011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20231023) 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, 1175 + ... + 6468.

It is an arithmetic number, because the mean of its divisors is an integer number (5060328).

Almost surely, 2^20231021 is an apocalyptic number.

It is an amenable number.

20231021 is a deficient number, since it is larger than the sum of its proper divisors (10291).

20231021 is an equidigital number, since it uses as much as digits as its factorization.

20231021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10290.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 20231021 is about 4497.8907278857. The cubic root of 20231021 is about 272.4829088964.

Adding to 20231021 its reverse (12013202), we get a palindrome (32244223).

The spelling of 20231021 in words is "twenty million, two hundred thirty-one thousand, twenty-one".