1221222100 has 54 divisors (see below), whose sum is σ = 3082725870. Its totient is φ = 418703040.

The previous prime is 1221222089. The next prime is 1221222113. The reversal of 1221222100 is 12221221.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 359329936 + 861892164 = 18956^2 + 29358^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 119715 + ... + 129514.

Almost surely, 2^1221222100 is an apocalyptic number.

1221222100 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221222100 is an abundant number, since it is smaller than the sum of its proper divisors (1861503770).

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

1221222100 is a wasteful number, since it uses less digits than its factorization.

1221222100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 249257 (or 249243 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 1221222100 is about 34945.9883248421. The cubic root of 1221222100 is about 1068.8864007481.

Adding to 1221222100 its reverse (12221221), we get a palindrome (1233443321).

The spelling of 1221222100 in words is "one billion, two hundred twenty-one million, two hundred twenty-two thousand, one hundred".