1661649 has 16 divisors (see below), whose sum is σ = 2475264. Its totient is φ = 982800.

The previous prime is 1661641. The next prime is 1661659. The reversal of 1661649 is 9461661.

It is not a de Polignac number, because 1661649 - 2³ = 1661641 is a prime.

It is a super-2 number, since 2×1661649² = 5522154798402, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 834 + ... + 2004.

It is an arithmetic number, because the mean of its divisors is an integer number (154704).

2^1661649 is an apocalyptic number.

It is an amenable number.

1661649 is a deficient number, since it is larger than the sum of its proper divisors (813615).

1661649 is a wasteful number, since it uses less digits than its factorization.

1661649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1228.

The product of its digits is 7776, while the sum is 33.

The square root of 1661649 is about 1289.0496499360. The cubic root of 1661649 is about 118.4440085140. Note that the first 3 decimals are identical.

The spelling of 1661649 in words is "one million, six hundred sixty-one thousand, six hundred forty-nine".