1001661661 has 64 divisors (see below), whose sum is σ = 1417973760. Its totient is φ = 682007040.

The previous prime is 1001661649. The next prime is 1001661721. The reversal of 1001661661 is 1661661001.

1001661661 is a nontrivial binomial coefficient, being equal to C(44759, 2).

It is not a de Polignac number, because 1001661661 - 2⁷ = 1001661533 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1001661631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 3200041 + ... + 3200353.

It is an arithmetic number, because the mean of its divisors is an integer number (22155840).

Almost surely, 2^1001661661 is an apocalyptic number.

1001661661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1001661661 is the 44758-th triangular number.

1001661661 is the 14920-th centered nonagonal number.

It is an amenable number.

1001661661 is a deficient number, since it is larger than the sum of its proper divisors (416312099).

1001661661 is a wasteful number, since it uses less digits than its factorization.

1001661661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 506.

The product of its (nonzero) digits is 1296, while the sum is 28.

The square root of 1001661661 is about 31649.0388637633. The cubic root of 1001661661 is about 1000.5535804921.

The spelling of 1001661661 in words is "one billion, one million, six hundred sixty-one thousand, six hundred sixty-one".