1128729821 has 4 divisors (see below), whose sum is σ = 1134459612. Its totient is φ = 1123000032.

The previous prime is 1128729799. The next prime is 1128729829. The reversal of 1128729821 is 1289278211.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 494395225 + 634334596 = 22235^2 + 25186^2 .

It is a cyclic number.

It is not a de Polignac number, because 1128729821 - 2¹⁸ = 1128467677 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1128729829) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2864600 + ... + 2864993.

It is an arithmetic number, because the mean of its divisors is an integer number (283614903).

Almost surely, 2^1128729821 is an apocalyptic number.

It is an amenable number.

1128729821 is a deficient number, since it is larger than the sum of its proper divisors (5729791).

1128729821 is an equidigital number, since it uses as much as digits as its factorization.

1128729821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5729790.

The product of its digits is 32256, while the sum is 41.

The square root of 1128729821 is about 33596.5745426524. The cubic root of 1128729821 is about 1041.1900273913.

The spelling of 1128729821 in words is "one billion, one hundred twenty-eight million, seven hundred twenty-nine thousand, eight hundred twenty-one".