661667 has 4 divisors (see below), whose sum is σ = 672576. Its totient is φ = 650760.

The previous prime is 661663. The next prime is 661673. The reversal of 661667 is 766166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 766166 = 2 ⋅383083.

It is a cyclic number.

It is not a de Polignac number, because 661667 - 2² = 661663 is a prime.

It is a Duffinian number.

It is a plaindrome in base 12.

It is not an unprimeable number, because it can be changed into a prime (661663) 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, 5363 + ... + 5484.

It is an arithmetic number, because the mean of its divisors is an integer number (168144).

2⁶⁶¹⁶⁶⁷ is an apocalyptic number.

661667 is a deficient number, since it is larger than the sum of its proper divisors (10909).

661667 is a wasteful number, since it uses less digits than its factorization.

661667 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10908.

The product of its digits is 9072, while the sum is 32.

The square root of 661667 is about 813.4291610214. The cubic root of 661667 is about 87.1391177162.

The spelling of 661667 in words is "six hundred sixty-one thousand, six hundred sixty-seven".