1289721 has 4 divisors (see below), whose sum is σ = 1719632. Its totient is φ = 859812.

The previous prime is 1289713. The next prime is 1289731. The reversal of 1289721 is 1279821.

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.

It is not a de Polignac number, because 1289721 - 2³ = 1289713 is a prime.

It is a D-number.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1289711) 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, 214951 + ... + 214956.

It is an arithmetic number, because the mean of its divisors is an integer number (429908).

2^1289721 is an apocalyptic number.

It is an amenable number.

1289721 is a deficient number, since it is larger than the sum of its proper divisors (429911).

1289721 is an equidigital number, since it uses as much as digits as its factorization.

1289721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 429910.

The product of its digits is 2016, while the sum is 30.

The square root of 1289721 is about 1135.6588396169. The cubic root of 1289721 is about 108.8508748250.

The spelling of 1289721 in words is "one million, two hundred eighty-nine thousand, seven hundred twenty-one".