661776 has 40 divisors (see below), whose sum is σ = 1812384. Its totient is φ = 207360.

The previous prime is 661769. The next prime is 661777. The reversal of 661776 is 677166.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661777) by changing a digit.

661776 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 411 + ... + 1221.

2⁶⁶¹⁷⁷⁶ is an apocalyptic number.

661776 is the 515-th centered pentagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661776, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (906192).

661776 is an abundant number, since it is smaller than the sum of its proper divisors (1150608).

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

661776 is a wasteful number, since it uses less digits than its factorization.

661776 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 839 (or 833 counting only the distinct ones).

The product of its digits is 10584, while the sum is 33.

The square root of 661776 is about 813.4961585650. The cubic root of 661776 is about 87.1439024202.

The spelling of 661776 in words is "six hundred sixty-one thousand, seven hundred seventy-six".