1661001661 has 16 divisors (see below), whose sum is σ = 1842247296. Its totient is φ = 1485000000.

The previous prime is 1661001599. The next prime is 1661001739.

1661001661 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 1661001661 - 2²⁷ = 1526783933 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661401661) 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 15 ways as a sum of consecutive naturals, for example, 162811 + ... + 172711.

It is an arithmetic number, because the mean of its divisors is an integer number (115140456).

Almost surely, 2^1661001661 is an apocalyptic number.

1661001661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1661001661 is a deficient number, since it is larger than the sum of its proper divisors (181245635).

1661001661 is a wasteful number, since it uses less digits than its factorization.

1661001661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10164.

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

The square root of 1661001661 is about 40755.3881223084. The cubic root of 1661001661 is about 1184.2862552498.

It can be divided in two parts, 166100 and 1661, that multiplied together give a square (275892100 = 16610²).

The spelling of 1661001661 in words is "one billion, six hundred sixty-one million, one thousand, six hundred sixty-one".