21201221000 has 64 divisors (see below), whose sum is σ = 50424294960. Its totient is φ = 8341440000.

The previous prime is 21201220981. The next prime is 21201221021. The reversal of 21201221000 is 12210212.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 211586116 + 20989634884 = 14546^2 + 144878^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 112781 + ... + 234780.

Almost surely, 2^21201221000 is an apocalyptic number.

21201221000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21201221000 is an abundant number, since it is smaller than the sum of its proper divisors (29223073960).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21201221000 is a wasteful number, since it uses less digits than its factorization.

21201221000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 347643 (or 347629 counting only the distinct ones).

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

Adding to 21201221000 its reverse (12210212), we get a palindrome (21213431212).

The spelling of 21201221000 in words is "twenty-one billion, two hundred one million, two hundred twenty-one thousand".