256541661 has 36 divisors (see below), whose sum is σ = 391711164. Its totient is φ = 167961600.

The previous prime is 256541657. The next prime is 256541669. The reversal of 256541661 is 166145652.

256541661 is a `hidden beast` number, since 2 + 56 + 541 + 6 + 61 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 110880900 + 145660761 = 10530^2 + 12069^2 .

It is not a de Polignac number, because 256541661 - 2² = 256541657 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (256541669) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 399901 + ... + 400541.

Almost surely, 2^256541661 is an apocalyptic number.

It is an amenable number.

256541661 is a deficient number, since it is larger than the sum of its proper divisors (135169503).

256541661 is an frugal number, since it uses more digits than its factorization.

256541661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 726 (or 705 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 256541661 is about 16016.9179619551. The cubic root of 256541661 is about 635.4079351223.

The spelling of 256541661 in words is "two hundred fifty-six million, five hundred forty-one thousand, six hundred sixty-one".