1661000661 has 10 divisors (see below), whose sum is σ = 2481248022. Its totient is φ = 1107333720.

The previous prime is 1661000641. The next prime is 1661000669. The reversal of 1661000661 is 1660001661.

It can be written as a sum of positive squares in only one way, i.e., 1405800036 + 255200625 = 37494^2 + 15975^2 .

It is not a de Polignac number, because 1661000661 - 2⁵ = 1661000629 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661000669) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 10253010 + ... + 10253171.

Almost surely, 2^1661000661 is an apocalyptic number.

It is an amenable number.

1661000661 is a deficient number, since it is larger than the sum of its proper divisors (820247361).

1661000661 is an equidigital number, since it uses as much as digits as its factorization.

1661000661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20506193 (or 20506184 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 1661000661 is about 40755.3758539901. The cubic root of 1661000661 is about 1184.2860175847.

It can be divided in two parts, 1661000 and 661, that added together give a palindrome (1661661).

The spelling of 1661000661 in words is "one billion, six hundred sixty-one million, six hundred sixty-one", and thus it is an aban number.