1221403128 has 64 divisors (see below), whose sum is σ = 3356622720. Its totient is φ = 367286400.

The previous prime is 1221403111. The next prime is 1221403129. The reversal of 1221403128 is 8213041221.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a junction number, because it is equal to n+sod(n) for n = 1221403098 and 1221403107.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221403129) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16926 + ... + 52242.

It is an arithmetic number, because the mean of its divisors is an integer number (52447230).

Almost surely, 2^1221403128 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1221403128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1678311360).

1221403128 is an abundant number, since it is smaller than the sum of its proper divisors (2135219592).

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

1221403128 is a wasteful number, since it uses less digits than its factorization.

1221403128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35468 (or 35464 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 1221403128 is about 34948.5783401843. The cubic root of 1221403128 is about 1068.9392136386.

Adding to 1221403128 its reverse (8213041221), we get a palindrome (9434444349).

The spelling of 1221403128 in words is "one billion, two hundred twenty-one million, four hundred three thousand, one hundred twenty-eight".