20731021 has 4 divisors (see below), whose sum is σ = 20741344. Its totient is φ = 20720700.

The previous prime is 20731001. The next prime is 20731043. The reversal of 20731021 is 12013702.

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: 12013702 = 2 ⋅6006851.

It is a cyclic number.

It is not a de Polignac number, because 20731021 - 2⁷ = 20730893 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20730986 and 20731004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20731001) 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, 1065 + ... + 6526.

It is an arithmetic number, because the mean of its divisors is an integer number (5185336).

Almost surely, 2^20731021 is an apocalyptic number.

It is an amenable number.

20731021 is a deficient number, since it is larger than the sum of its proper divisors (10323).

20731021 is an equidigital number, since it uses as much as digits as its factorization.

20731021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10322.

The product of its (nonzero) digits is 84, while the sum is 16.

The square root of 20731021 is about 4553.1330971102. The cubic root of 20731021 is about 274.7094275166.

Adding to 20731021 its reverse (12013702), we get a palindrome (32744723).

The spelling of 20731021 in words is "twenty million, seven hundred thirty-one thousand, twenty-one".