1221553100000 has 72 divisors (see below), whose sum is σ = 3005973683496. Its totient is φ = 488621200000.

The previous prime is 1221553099993. The next prime is 1221553100003. The reversal of 1221553100000 is 13551221.

It is a happy number.

It is a super-2 number, since 2×1221553100000² (a number of 25 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221553100003) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6007766 + ... + 6207765.

It is an arithmetic number, because the mean of its divisors is an integer number (41749634493).

Almost surely, 2^{1221553100000} is an apocalyptic number.

1221553100000 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221553100000 is an abundant number, since it is smaller than the sum of its proper divisors (1784420583496).

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

1221553100000 is an frugal number, since it uses more digits than its factorization.

1221553100000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12215566 (or 12215538 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 20.

Adding to 1221553100000 its reverse (13551221), we get a palindrome (1221566651221).

The spelling of 1221553100000 in words is "one trillion, two hundred twenty-one billion, five hundred fifty-three million, one hundred thousand".