1221211002100 has 36 divisors (see below), whose sum is σ = 2805911871084. Its totient is φ = 459750023680.

The previous prime is 1221211002097. The next prime is 1221211002103. The reversal of 1221211002100 is 12001121221.

It is an interprime number because it is at equal distance from previous prime (1221211002097) and next prime (1221211002103).

It can be written as a sum of positive squares in 6 ways, for example, as 60135791076 + 1161075211024 = 245226^2 + 1077532^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221211002103) 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, 359178007 + ... + 359181406.

It is an arithmetic number, because the mean of its divisors is an integer number (77941996419).

Almost surely, 2^{1221211002100} is an apocalyptic number.

1221211002100 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221211002100 is an abundant number, since it is smaller than the sum of its proper divisors (1584700868984).

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

1221211002100 is a wasteful number, since it uses less digits than its factorization.

1221211002100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 718359444 (or 718359437 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 1221211002100 its reverse (12001121221), we get a palindrome (1233212123321).

The spelling of 1221211002100 in words is "one trillion, two hundred twenty-one billion, two hundred eleven million, two thousand, one hundred".