661599 has 24 divisors (see below), whose sum is σ = 1038960. Its totient is φ = 404352.

The previous prime is 661553. The next prime is 661603. The reversal of 661599 is 995166.

661599 is a `hidden beast` number, since 6 + 61 + 599 = 666.

661599 is digitally balanced in base 2 and base 7, because in such bases it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 661599 - 2⁸ = 661343 is a prime.

661599 is strictly pandigital in base 7.

661599 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661099) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9027 + ... + 9099.

It is an arithmetic number, because the mean of its divisors is an integer number (43290).

2⁶⁶¹⁵⁹⁹ is an apocalyptic number.

661599 is a deficient number, since it is larger than the sum of its proper divisors (377361).

661599 is a wasteful number, since it uses less digits than its factorization.

661599 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151 (or 148 counting only the distinct ones).

The product of its digits is 14580, while the sum is 36.

The square root of 661599 is about 813.3873615935. The cubic root of 661599 is about 87.1361324970.

The spelling of 661599 in words is "six hundred sixty-one thousand, five hundred ninety-nine".