1221220221000 has 256 divisors, whose sum is σ = 4143151434240. Its totient is φ = 297688550400.

The previous prime is 1221220220993. The next prime is 1221220221007. The reversal of 1221220221000 is 1220221221.

It is an interprime number because it is at equal distance from previous prime (1221220220993) and next prime (1221220221007).

It is a Harshad number since it is a multiple of its sum of digits (15).

It is not an unprimeable number, because it can be changed into a prime (1221220221007) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 3864994 + ... + 4169006.

It is an arithmetic number, because the mean of its divisors is an integer number (16184185290).

Almost surely, 2^{1221220221000} is an apocalyptic number.

1221220221000 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 1221220221000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2071575717120).

1221220221000 is an abundant number, since it is smaller than the sum of its proper divisors (2921931213240).

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

1221220221000 is a wasteful number, since it uses less digits than its factorization.

1221220221000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 304153 (or 304139 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 15.

Adding to 1221220221000 its reverse (1220221221), we get a palindrome (1222440442221).

The spelling of 1221220221000 in words is "one trillion, two hundred twenty-one billion, two hundred twenty million, two hundred twenty-one thousand".