401661 has 12 divisors (see below), whose sum is σ = 624988. Its totient is φ = 247104.

The previous prime is 401651. The next prime is 401669. The reversal of 401661 is 166104.

401661 is a `hidden beast` number, since 4 + 0 + 1 + 661 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 93636 + 308025 = 306^2 + 555^2 .

It is not a de Polignac number, because 401661 - 2⁵ = 401629 is a prime.

It is a super-2 number, since 2×401661² = 322663117842, which contains 22 as substring.

It is a Curzon number.

It is a nialpdrome in base 14.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 401661.

It is not an unprimeable number, because it can be changed into a prime (401669) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1600 + ... + 1833.

2⁴⁰¹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

401661 is a deficient number, since it is larger than the sum of its proper divisors (223327).

401661 is a wasteful number, since it uses less digits than its factorization.

401661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3452 (or 3449 counting only the distinct ones).

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

The square root of 401661 is about 633.7673074560. The cubic root of 401661 is about 73.7824754036.

Adding to 401661 its reverse (166104), we get a palindrome (567765).

The spelling of 401661 in words is "four hundred one thousand, six hundred sixty-one".