1215561728 has 38 divisors (see below), whose sum is σ = 2431643106. Its totient is φ = 607649792.

The previous prime is 1215561713. The next prime is 1215561749. The reversal of 1215561728 is 8271655121.

It can be written as a sum of positive squares in only one way, i.e., 912523264 + 303038464 = 30208^2 + 17408^2 .

It is a junction number, because it is equal to n+sod(n) for n = 1215561691 and 1215561700.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 259826 + ... + 264462.

Almost surely, 2^1215561728 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 1215561728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1215821553).

1215561728 is an abundant number, since it is smaller than the sum of its proper divisors (1216081378).

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

1215561728 is an frugal number, since it uses more digits than its factorization.

1215561728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4673 (or 4639 counting only the distinct ones).

The product of its digits is 33600, while the sum is 38.

The square root of 1215561728 is about 34864.9068262056. The cubic root of 1215561728 is about 1067.2324109956.

The spelling of 1215561728 in words is "one billion, two hundred fifteen million, five hundred sixty-one thousand, seven hundred twenty-eight".