661807 has 4 divisors (see below), whose sum is σ = 675936. Its totient is φ = 647680.

The previous prime is 661777. The next prime is 661823. The reversal of 661807 is 708166.

661807 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.

It is a cyclic number.

It is not a de Polignac number, because 661807 - 2⁷ = 661679 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 (661877) 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, 6994 + ... + 7087.

It is an arithmetic number, because the mean of its divisors is an integer number (168984).

2⁶⁶¹⁸⁰⁷ is an apocalyptic number.

661807 is a deficient number, since it is larger than the sum of its proper divisors (14129).

661807 is a wasteful number, since it uses less digits than its factorization.

661807 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14128.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 661807 is about 813.5152119045. The cubic root of 661807 is about 87.1452631117.

The spelling of 661807 in words is "six hundred sixty-one thousand, eight hundred seven".