21203221221 has 72 divisors (see below), whose sum is σ = 38742971904. Its totient is φ = 10881267840.

The previous prime is 21203221213. The next prime is 21203221231. The reversal of 21203221221 is 12212230212.

21203221221 is a `hidden beast` number, since 2 + 120 + 322 + 1 + 221 = 666.

It is not a de Polignac number, because 21203221221 - 2³ = 21203221213 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21203221194 and 21203221203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21203221231) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 1111756 + ... + 1130666.

It is an arithmetic number, because the mean of its divisors is an integer number (538096832).

Almost surely, 2^21203221221 is an apocalyptic number.

21203221221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21203221221 is a deficient number, since it is larger than the sum of its proper divisors (17539750683).

21203221221 is a wasteful number, since it uses less digits than its factorization.

21203221221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19011 (or 18971 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

Adding to 21203221221 its reverse (12212230212), we get a palindrome (33415451433).

The spelling of 21203221221 in words is "twenty-one billion, two hundred three million, two hundred twenty-one thousand, two hundred twenty-one".