309661 has 4 divisors (see below), whose sum is σ = 337824. Its totient is φ = 281500.

The previous prime is 309637. The next prime is 309667. The reversal of 309661 is 166903.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 166903 = 11 ⋅15173.

It is a cyclic number.

It is not a de Polignac number, because 309661 - 2⁵ = 309629 is a prime.

It is a Duffinian number.

309661 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (309667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14065 + ... + 14086.

It is an arithmetic number, because the mean of its divisors is an integer number (84456).

2³⁰⁹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

309661 is a deficient number, since it is larger than the sum of its proper divisors (28163).

309661 is a wasteful number, since it uses less digits than its factorization.

309661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28162.

The product of its (nonzero) digits is 972, while the sum is 25.

The square root of 309661 is about 556.4719220230. The cubic root of 309661 is about 67.6543154379.

The spelling of 309661 in words is "three hundred nine thousand, six hundred sixty-one".