661878 has 64 divisors (see below), whose sum is σ = 1797120. Its totient is φ = 176256.

The previous prime is 661877. The next prime is 661879. The reversal of 661878 is 878166.

661878 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (661877) and next prime (661879).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661873) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6375 + ... + 6477.

It is an arithmetic number, because the mean of its divisors is an integer number (28080).

2⁶⁶¹⁸⁷⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661878, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (898560).

661878 is an abundant number, since it is smaller than the sum of its proper divisors (1135242).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661878 is a wasteful number, since it uses less digits than its factorization.

661878 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 138 (or 132 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 661878 is about 813.5588485168. The cubic root of 661878 is about 87.1483793739.

The spelling of 661878 in words is "six hundred sixty-one thousand, eight hundred seventy-eight".