661567 has 4 divisors (see below), whose sum is σ = 672840. Its totient is φ = 650296.

The previous prime is 661553. The next prime is 661603. The reversal of 661567 is 765166.

661567 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 765166 = 2 ⋅382583.

It is a cyclic number.

It is not a de Polignac number, because 661567 - 2⁷ = 661439 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661517) 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, 5548 + ... + 5665.

It is an arithmetic number, because the mean of its divisors is an integer number (168210).

2⁶⁶¹⁵⁶⁷ is an apocalyptic number.

661567 is a deficient number, since it is larger than the sum of its proper divisors (11273).

661567 is a wasteful number, since it uses less digits than its factorization.

661567 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11272.

The product of its digits is 7560, while the sum is 31.

The square root of 661567 is about 813.3676905312. The cubic root of 661567 is about 87.1347276173.

The spelling of 661567 in words is "six hundred sixty-one thousand, five hundred sixty-seven".