1221312120 has 64 divisors (see below), whose sum is σ = 4187358720. Its totient is φ = 279156864.

The previous prime is 1221312091. The next prime is 1221312149. The reversal of 1221312120 is 212131221.

It is an interprime number because it is at equal distance from previous prime (1221312091) and next prime (1221312149).

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 1221312120.

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 15 ways as a sum of consecutive naturals, for example, 726132 + ... + 727811.

It is an arithmetic number, because the mean of its divisors is an integer number (65427480).

Almost surely, 2^1221312120 is an apocalyptic number.

1221312120 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221312120 is an abundant number, since it is smaller than the sum of its proper divisors (2966046600).

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

1221312120 is a wasteful number, since it uses less digits than its factorization.

1221312120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1453964 (or 1453960 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 15.

The square root of 1221312120 is about 34947.2762887181. The cubic root of 1221312120 is about 1068.9126637267.

Adding to 1221312120 its reverse (212131221), we get a palindrome (1433443341).

It can be divided in two parts, 122131 and 2120, that added together give a triangular number (124251 = T₄₉₈).

The spelling of 1221312120 in words is "one billion, two hundred twenty-one million, three hundred twelve thousand, one hundred twenty".