1221222555 has 128 divisors (see below), whose sum is σ = 2600294400. Its totient is φ = 532127232.

The previous prime is 1221222551. The next prime is 1221222581. The reversal of 1221222555 is 5552221221.

It is a happy number.

It is not a de Polignac number, because 1221222555 - 2² = 1221222551 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (1221222551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 1852816 + ... + 1853474.

It is an arithmetic number, because the mean of its divisors is an integer number (20314800).

Almost surely, 2^1221222555 is an apocalyptic number.

1221222555 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

1221222555 is an abundant number, since it is smaller than the sum of its proper divisors (1379071845).

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

1221222555 is a wasteful number, since it uses less digits than its factorization.

1221222555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 770 (or 764 counting only the distinct ones).

The product of its digits is 4000, while the sum is 27.

The square root of 1221222555 is about 34945.9948348877. The cubic root of 1221222555 is about 1068.8865334958.

Adding to 1221222555 its reverse (5552221221), we get a palindrome (6773443776).

The spelling of 1221222555 in words is "one billion, two hundred twenty-one million, two hundred twenty-two thousand, five hundred fifty-five".