1221100021000 has 128 divisors (see below), whose sum is σ = 3026276004960. Its totient is φ = 459583488000.

The previous prime is 1221100020977. The next prime is 1221100021013. The reversal of 1221100021000 is 1200011221.

It can be written as a sum of positive squares in 16 ways, for example, as 5095389924 + 1216004631076 = 71382^2 + 1102726^2 .

It is a super-2 number, since 2×1221100021000² (a number of 25 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 83853720 + ... + 83868280.

Almost surely, 2^{1221100021000} is an apocalyptic number.

1221100021000 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 1221100021000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1513138002480).

1221100021000 is an abundant number, since it is smaller than the sum of its proper divisors (1805175983960).

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

1221100021000 is a wasteful number, since it uses less digits than its factorization.

1221100021000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19532 (or 19518 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 1221100021000 its reverse (1200011221), we get a palindrome (1222300032221).

The spelling of 1221100021000 in words is "one trillion, two hundred twenty-one billion, one hundred million, twenty-one thousand".