1221221012100 has 72 divisors (see below), whose sum is σ = 3628896777408. Its totient is φ = 316857340800.

The previous prime is 1221221012059. The next prime is 1221221012119. The reversal of 1221221012100 is 12101221221.

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

It is a self number, because there is not a number n which added to its sum of digits gives 1221221012100.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 54998856 + ... + 55021055.

Almost surely, 2^{1221221012100} is an apocalyptic number.

1221221012100 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221221012100 is an abundant number, since it is smaller than the sum of its proper divisors (2407675765308).

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

1221221012100 is a wasteful number, since it uses less digits than its factorization.

1221221012100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 110019965 (or 110019958 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 15.

Adding to 1221221012100 its reverse (12101221221), we get a palindrome (1233322233321).

The spelling of 1221221012100 in words is "one trillion, two hundred twenty-one billion, two hundred twenty-one million, twelve thousand, one hundred".