661825 has 12 divisors (see below), whose sum is σ = 857088. Its totient is φ = 506000.

The previous prime is 661823. The next prime is 661849. The reversal of 661825 is 528166.

661825 is a nontrivial binomial coefficient, being equal to C(1151, 2).

It is not a de Polignac number, because 661825 - 2¹ = 661823 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 661793 and 661802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1 + ... + 1150.

It is an arithmetic number, because the mean of its divisors is an integer number (71424).

2⁶⁶¹⁸²⁵ is an apocalyptic number.

661825 is the 1150-th triangular number.

661825 is the 384-th centered nonagonal number.

It is an amenable number.

661825 is a deficient number, since it is larger than the sum of its proper divisors (195263).

661825 is a wasteful number, since it uses less digits than its factorization.

661825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1184 (or 1179 counting only the distinct ones).

The product of its digits is 2880, while the sum is 28.

The square root of 661825 is about 813.5262749291. The cubic root of 661825 is about 87.1460531711.

It can be divided in two parts, 66 and 1825, that added together give a triangular number (1891 = T₆₁).

The spelling of 661825 in words is "six hundred sixty-one thousand, eight hundred twenty-five".