1684721 has 4 divisors (see below), whose sum is σ = 1730292. Its totient is φ = 1639152.

The previous prime is 1684703. The next prime is 1684733. The reversal of 1684721 is 1274861.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1274861 = 7 ⋅182123.

It can be written as a sum of positive squares in 2 ways, for example, as 1210000 + 474721 = 1100^2 + 689^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1684721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1684741) 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, 22730 + ... + 22803.

It is an arithmetic number, because the mean of its divisors is an integer number (432573).

2^1684721 is an apocalyptic number.

It is an amenable number.

1684721 is a deficient number, since it is larger than the sum of its proper divisors (45571).

1684721 is an equidigital number, since it uses as much as digits as its factorization.

1684721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45570.

The product of its digits is 2688, while the sum is 29.

The square root of 1684721 is about 1297.9680273412. The cubic root of 1684721 is about 118.9896891003.

The spelling of 1684721 in words is "one million, six hundred eighty-four thousand, seven hundred twenty-one".