20021001221 has 4 divisors (see below), whose sum is σ = 21561078252. Its totient is φ = 18480924192.

The previous prime is 20021001193. The next prime is 20021001229. The reversal of 20021001221 is 12210012002.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12210012002 = 2 ⋅6105006001.

It can be written as a sum of positive squares in 2 ways, for example, as 3607804225 + 16413196996 = 60065^2 + 128114^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20021001221 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 (20021001229) 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, 770038496 + ... + 770038521.

It is an arithmetic number, because the mean of its divisors is an integer number (5390269563).

Almost surely, 2^20021001221 is an apocalyptic number.

It is an amenable number.

20021001221 is a deficient number, since it is larger than the sum of its proper divisors (1540077031).

20021001221 is a wasteful number, since it uses less digits than its factorization.

20021001221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1540077030.

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 20021001221 its reverse (12210012002), we get a palindrome (32231013223).

The spelling of 20021001221 in words is "twenty billion, twenty-one million, one thousand, two hundred twenty-one".