20501221221 has 24 divisors (see below), whose sum is σ = 31928330616. Its totient is φ = 12601284480.

The previous prime is 20501221219. The next prime is 20501221229. The reversal of 20501221221 is 12212210502.

20501221221 is a `hidden beast` number, since 20 + 501 + 22 + 122 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 333245025 + 20167976196 = 18255^2 + 142014^2 .

It is not a de Polignac number, because 20501221221 - 2¹ = 20501221219 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20501221194 and 20501221203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20501221229) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2910 + ... + 202511.

It is an arithmetic number, because the mean of its divisors is an integer number (1330347109).

Almost surely, 2^20501221221 is an apocalyptic number.

It is an amenable number.

20501221221 is a deficient number, since it is larger than the sum of its proper divisors (11427109395).

20501221221 is a wasteful number, since it uses less digits than its factorization.

20501221221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206293 (or 206290 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

Adding to 20501221221 its reverse (12212210502), we get a palindrome (32713431723).

The spelling of 20501221221 in words is "twenty billion, five hundred one million, two hundred twenty-one thousand, two hundred twenty-one".