4001661 has 24 divisors (see below), whose sum is σ = 6064344. Its totient is φ = 2540160.

The previous prime is 4001639. The next prime is 4001689. The reversal of 4001661 is 1661004.

4001661 is a `hidden beast` number, since 4 + 0 + 0 + 1 + 661 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 1425636 + 2576025 = 1194^2 + 1605^2 .

It is not a de Polignac number, because 4001661 - 2⁵ = 4001629 is a prime.

It is a super-3 number, since 3×4001661³ (a number of 21 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (4001611) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 20215 + ... + 20411.

It is an arithmetic number, because the mean of its divisors is an integer number (252681).

Almost surely, 2^4001661 is an apocalyptic number.

It is an amenable number.

4001661 is a deficient number, since it is larger than the sum of its proper divisors (2062683).

4001661 is a wasteful number, since it uses less digits than its factorization.

4001661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 301 (or 298 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 4001661 is about 2000.4152069008. The cubic root of 4001661 is about 158.7620744324.

Adding to 4001661 its reverse (1661004), we get a palindrome (5662665).

The spelling of 4001661 in words is "four million, one thousand, six hundred sixty-one".