1606721 has 4 divisors (see below), whose sum is σ = 1701252. Its totient is φ = 1512192.

The previous prime is 1606681. The next prime is 1606723. The reversal of 1606721 is 1276061.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1276061 = 827 ⋅1543.

It can be written as a sum of positive squares in 2 ways, for example, as 1345600 + 261121 = 1160^2 + 511^2 .

It is a cyclic number.

It is not a de Polignac number, because 1606721 - 2¹⁰ = 1605697 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 (1606723) 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, 47240 + ... + 47273.

It is an arithmetic number, because the mean of its divisors is an integer number (425313).

2^1606721 is an apocalyptic number.

It is an amenable number.

1606721 is a deficient number, since it is larger than the sum of its proper divisors (94531).

1606721 is an equidigital number, since it uses as much as digits as its factorization.

1606721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 94530.

The product of its (nonzero) digits is 504, while the sum is 23.

The square root of 1606721 is about 1267.5649884720. The cubic root of 1606721 is about 117.1242501111.

The spelling of 1606721 in words is "one million, six hundred six thousand, seven hundred twenty-one".