1221121000 has 128 divisors (see below), whose sum is σ = 3218641920. Its totient is φ = 429600000.

The previous prime is 1221120961. The next prime is 1221121001. The reversal of 1221121000 is 1211221.

It is a super-2 number, since 2×1221121000² = 2982272993282000000, which contains 22 as substring.

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

It is not an unprimeable number, because it can be changed into a prime (1221121001) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 339210 + ... + 342790.

It is an arithmetic number, because the mean of its divisors is an integer number (25145640).

Almost surely, 2^1221121000 is an apocalyptic number.

1221121000 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 1221121000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1609320960).

1221121000 is an abundant number, since it is smaller than the sum of its proper divisors (1997520920).

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

1221121000 is a wasteful number, since it uses less digits than its factorization.

1221121000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3644 (or 3630 counting only the distinct ones).

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

The square root of 1221121000 is about 34944.5417769356. The cubic root of 1221121000 is about 1068.8569036846.

Adding to 1221121000 its reverse (1211221), we get a palindrome (1222332221).

It can be divided in two parts, 1221 and 121000, that added together give a palindrome (122221).

The spelling of 1221121000 in words is "one billion, two hundred twenty-one million, one hundred twenty-one thousand".