1661641 has 2 divisors, whose sum is σ = 1661642. Its totient is φ = 1661640.

The previous prime is 1661629. The next prime is 1661659. The reversal of 1661641 is 1461661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1177225 + 484416 = 1085^2 + 696^2 .

It is an emirp because it is prime and its reverse (1461661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1661641 - 2¹⁵ = 1628873 is a prime.

It is a super-2 number, since 2×1661641² = 5522101625762, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1661141) 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 as a sum of consecutive naturals, namely, 830820 + 830821.

It is an arithmetic number, because the mean of its divisors is an integer number (830821).

2^1661641 is an apocalyptic number.

It is an amenable number.

1661641 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661641 is an equidigital number, since it uses as much as digits as its factorization.

1661641 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 864, while the sum is 25.

The square root of 1661641 is about 1289.0465468710. The cubic root of 1661641 is about 118.4438184310.

The spelling of 1661641 in words is "one million, six hundred sixty-one thousand, six hundred forty-one".