20513321 has 4 divisors (see below), whose sum is σ = 20522832. Its totient is φ = 20503812.

The previous prime is 20513303. The next prime is 20513327. The reversal of 20513321 is 12331502.

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: 12331502 = 2 ⋅6165751.

It is a cyclic number.

It is not a de Polignac number, because 20513321 - 2⁶ = 20513257 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20513321.

It is not an unprimeable number, because it can be changed into a prime (20513327) 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, 206 + ... + 6408.

It is an arithmetic number, because the mean of its divisors is an integer number (5130708).

Almost surely, 2^20513321 is an apocalyptic number.

It is an amenable number.

20513321 is a deficient number, since it is larger than the sum of its proper divisors (9511).

20513321 is an equidigital number, since it uses as much as digits as its factorization.

20513321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9510.

The product of its (nonzero) digits is 180, while the sum is 17.

The square root of 20513321 is about 4529.1633885299. The cubic root of 20513321 is about 273.7444515601.

Adding to 20513321 its reverse (12331502), we get a palindrome (32844823).

The spelling of 20513321 in words is "twenty million, five hundred thirteen thousand, three hundred twenty-one".