1648721 has 4 divisors (see below), whose sum is σ = 1664832. Its totient is φ = 1632612.

The previous prime is 1648697. The next prime is 1648723. The reversal of 1648721 is 1278461.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1648721 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1648723) 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, 7901 + ... + 8106.

It is an arithmetic number, because the mean of its divisors is an integer number (416208).

2^1648721 is an apocalyptic number.

It is an amenable number.

1648721 is a deficient number, since it is larger than the sum of its proper divisors (16111).

1648721 is a wasteful number, since it uses less digits than its factorization.

1648721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16110.

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

The square root of 1648721 is about 1284.0253112770. The cubic root of 1648721 is about 118.1360348211.

The spelling of 1648721 in words is "one million, six hundred forty-eight thousand, seven hundred twenty-one".