1647661 has 4 divisors (see below), whose sum is σ = 1734400. Its totient is φ = 1560924.

The previous prime is 1647649. The next prime is 1647673. The reversal of 1647661 is 1667461.

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 an interprime number because it is at equal distance from previous prime (1647649) and next prime (1647673).

It is a cyclic number.

It is not a de Polignac number, because 1647661 - 2¹¹ = 1645613 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1647601) 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, 43341 + ... + 43378.

It is an arithmetic number, because the mean of its divisors is an integer number (433600).

2^1647661 is an apocalyptic number.

It is an amenable number.

1647661 is a deficient number, since it is larger than the sum of its proper divisors (86739).

1647661 is an equidigital number, since it uses as much as digits as its factorization.

1647661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86738.

The product of its digits is 6048, while the sum is 31.

The square root of 1647661 is about 1283.6124804629. The cubic root of 1647661 is about 118.1107119510.

The spelling of 1647661 in words is "one million, six hundred forty-seven thousand, six hundred sixty-one".