20321221 has 4 divisors (see below), whose sum is σ = 20398752. Its totient is φ = 20243692.

The previous prime is 20321201. The next prime is 20321233. The reversal of 20321221 is 12212302.

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 an emirpimes, since its reverse is a distinct semiprime: 12212302 = 2 ⋅6106151.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20321221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20321201) 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, 38371 + ... + 38896.

It is an arithmetic number, because the mean of its divisors is an integer number (5099688).

Almost surely, 2^20321221 is an apocalyptic number.

It is an amenable number.

20321221 is a deficient number, since it is larger than the sum of its proper divisors (77531).

20321221 is an equidigital number, since it uses as much as digits as its factorization.

20321221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77530.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 20321221 is about 4507.9064985867. The cubic root of 20321221 is about 272.8872635365.

Adding to 20321221 its reverse (12212302), we get a palindrome (32533523).

The spelling of 20321221 in words is "twenty million, three hundred twenty-one thousand, two hundred twenty-one".