21221204210 has 16 divisors (see below), whose sum is σ = 40445118936. Its totient is φ = 7989159168.

The previous prime is 21221204167. The next prime is 21221204267. The reversal of 21221204210 is 1240212212.

It can be written as a sum of positive squares in 4 ways, for example, as 19926427921 + 1294776289 = 141161^2 + 35983^2 .

It is a Harshad number since it is a multiple of its sum of digits (17).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 62415137 + ... + 62415476.

Almost surely, 2^21221204210 is an apocalyptic number.

21221204210 is a deficient number, since it is larger than the sum of its proper divisors (19223914726).

21221204210 is a wasteful number, since it uses less digits than its factorization.

21221204210 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 124830637.

The product of its (nonzero) digits is 128, while the sum is 17.

Adding to 21221204210 its reverse (1240212212), we get a palindrome (22461416422).

The spelling of 21221204210 in words is "twenty-one billion, two hundred twenty-one million, two hundred four thousand, two hundred ten".