1128721 has 4 divisors (see below), whose sum is σ = 1231344. Its totient is φ = 1026100.

The previous prime is 1128719. The next prime is 1128727. The reversal of 1128721 is 1278211.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1278211 = 11 ⋅116201.

It is a cyclic number.

It is not a de Polignac number, because 1128721 - 2¹ = 1128719 is a prime.

It is a super-2 number, since 2×1128721² = 2548022191682, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1128692 and 1128701.

It is not an unprimeable number, because it can be changed into a prime (1128727) 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, 51295 + ... + 51316.

It is an arithmetic number, because the mean of its divisors is an integer number (307836).

2^1128721 is an apocalyptic number.

1128721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1128721 is a deficient number, since it is larger than the sum of its proper divisors (102623).

1128721 is a wasteful number, since it uses less digits than its factorization.

1128721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 102622.

The product of its digits is 224, while the sum is 22.

The square root of 1128721 is about 1062.4128199528. The cubic root of 1128721 is about 104.1187315091.

It can be divided in two parts, 1128 and 721, that added together give a square (1849 = 43²).

The spelling of 1128721 in words is "one million, one hundred twenty-eight thousand, seven hundred twenty-one".