1220421555 has 24 divisors (see below), whose sum is σ = 2121520752. Its totient is φ = 649007424.

The previous prime is 1220421541. The next prime is 1220421557. The reversal of 1220421555 is 5551240221.

It is not a de Polignac number, because 1220421555 - 2⁶ = 1220421491 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1220421557) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 23464 + ... + 54693.

It is an arithmetic number, because the mean of its divisors is an integer number (88396698).

Almost surely, 2^1220421555 is an apocalyptic number.

1220421555 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

1220421555 is a deficient number, since it is larger than the sum of its proper divisors (901099197).

1220421555 is a wasteful number, since it uses less digits than its factorization.

1220421555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78515 (or 78512 counting only the distinct ones).

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

The square root of 1220421555 is about 34934.5324142173. The cubic root of 1220421555 is about 1068.6527881212.

Adding to 1220421555 its reverse (5551240221), we get a palindrome (6771661776).

It can be divided in two parts, 12204215 and 55, that added together give a triangular number (12204270 = T₄₉₄₀).

The spelling of 1220421555 in words is "one billion, two hundred twenty million, four hundred twenty-one thousand, five hundred fifty-five".