1221000000 has 392 divisors, whose sum is σ = 4524317088. Its totient is φ = 288000000.

The previous prime is 1220999999. The next prime is 1221000017. The reversal of 1221000000 is 1221.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (6).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 32999982 + ... + 33000018.

Almost surely, 2^1221000000 is an apocalyptic number.

1221000000 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 1221000000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2262158544).

1221000000 is an abundant number, since it is smaller than the sum of its proper divisors (3303317088).

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

1221000000 is an frugal number, since it uses more digits than its factorization.

1221000000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93 (or 58 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 6.

The square root of 1221000000 is about 34942.8104193123. The cubic root of 1221000000 is about 1068.8215984317.

Adding to 1221000000 its reverse (1221), we get a palindrome (1221001221).

Multiplying 1221000000 by its reverse (1221), we get a square (1490841000000 = 1221000²).

1221000000 divided by its reverse (1221) gives a 6-th power (1000000 = 10⁶).

It can be divided in two parts, 12 and 21000000, that added together give a palindrome (21000012).

The spelling of 1221000000 in words is "one billion, two hundred twenty-one million", and thus it is an aban number.