661788 has 36 divisors (see below), whose sum is σ = 1729728. Its totient is φ = 213120.

The previous prime is 661777. The next prime is 661823. The reversal of 661788 is 887166.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an Ulam number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 820 + ... + 1412.

It is an arithmetic number, because the mean of its divisors is an integer number (48048).

2⁶⁶¹⁷⁸⁸ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661788, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (864864).

661788 is an abundant number, since it is smaller than the sum of its proper divisors (1067940).

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

661788 is a wasteful number, since it uses less digits than its factorization.

661788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 634 (or 629 counting only the distinct ones).

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

The square root of 661788 is about 813.5035341042. The cubic root of 661788 is about 87.1444291445.

The spelling of 661788 in words is "six hundred sixty-one thousand, seven hundred eighty-eight".