1221221000 has 32 divisors (see below), whose sum is σ = 2857659480. Its totient is φ = 488488000.

The previous prime is 1221220981. The next prime is 1221221003. The reversal of 1221221000 is 1221221.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 810996484 + 410224516 = 28478^2 + 20254^2 .

It is not an unprimeable number, because it can be changed into a prime (1221221003) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 609611 + ... + 611610.

Almost surely, 2^1221221000 is an apocalyptic number.

1221221000 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221221000 is an abundant number, since it is smaller than the sum of its proper divisors (1636438480).

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

1221221000 is a wasteful number, since it uses less digits than its factorization.

1221221000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1221242 (or 1221228 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 1221221000 is about 34945.9725862652. The cubic root of 1221221000 is about 1068.8860798194.

Adding to 1221221000 its reverse (1221221), we get a palindrome (1222442221).

1221221000 divided by its reverse (1221221) gives a cube (1000 = 10³).

The spelling of 1221221000 in words is "one billion, two hundred twenty-one million, two hundred twenty-one thousand".