75661 has 4 divisors (see below), whose sum is σ = 78300. Its totient is φ = 73024.

The previous prime is 75659. The next prime is 75679. The reversal of 75661 is 16657.

75661 = 194² + 195².

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 38025 + 37636 = 195^2 + 194^2 .

It is a cyclic number.

It is not a de Polignac number, because 75661 - 2¹ = 75659 is a prime.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (75611) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1276 + ... + 1333.

It is an arithmetic number, because the mean of its divisors is an integer number (19575).

2⁷⁵⁶⁶¹ is an apocalyptic number.

75661 is the 195-th centered square number.

It is an amenable number.

75661 is a deficient number, since it is larger than the sum of its proper divisors (2639).

75661 is a wasteful number, since it uses less digits than its factorization.

75661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2638.

The product of its digits is 1260, while the sum is 25.

The square root of 75661 is about 275.0654467577. The cubic root of 75661 is about 42.2951619599.

The spelling of 75661 in words is "seventy-five thousand, six hundred sixty-one".