1221105655 has 64 divisors (see below), whose sum is σ = 1906384896. Its totient is φ = 728640000.

The previous prime is 1221105649. The next prime is 1221105689. The reversal of 1221105655 is 5565011221.

It is not a de Polignac number, because 1221105655 - 2³ = 1221105647 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1204929 + ... + 1205941.

It is an arithmetic number, because the mean of its divisors is an integer number (29787264).

Almost surely, 2^1221105655 is an apocalyptic number.

1221105655 is a deficient number, since it is larger than the sum of its proper divisors (685279241).

1221105655 is a wasteful number, since it uses less digits than its factorization.

1221105655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1168.

The product of its (nonzero) digits is 3000, while the sum is 28.

The square root of 1221105655 is about 34944.3222140593. The cubic root of 1221105655 is about 1068.8524264658.

Adding to 1221105655 its reverse (5565011221), we get a palindrome (6786116876).

It can be divided in two parts, 122110 and 5655, that added together give a triangular number (127765 = T₅₀₅).

The spelling of 1221105655 in words is "one billion, two hundred twenty-one million, one hundred five thousand, six hundred fifty-five".