1221221001000 has 2048 divisors, whose sum is σ = 5449586688000. Its totient is φ = 219469824000.

The previous prime is 1221221000977. The next prime is 1221221001001. The reversal of 1221221001000 is 1001221221.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is not an unprimeable number, because it can be changed into a prime (1221221001001) by changing a digit.

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 511 ways as a sum of consecutive naturals, for example, 3222218811 + ... + 3222219189.

It is an arithmetic number, because the mean of its divisors is an integer number (2660931000).

Almost surely, 2^{1221221001000} is an apocalyptic number.

1221221001000 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1221221001000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2724793344000).

1221221001000 is an abundant number, since it is smaller than the sum of its proper divisors (4228365687000).

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

1221221001000 is a wasteful number, since it uses less digits than its factorization.

1221221001000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 500 (or 486 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 1221221001000 its reverse (1001221221), we get a palindrome (1222222222221).

The spelling of 1221221001000 in words is "one trillion, two hundred twenty-one billion, two hundred twenty-one million, one thousand".