661375 has 32 divisors (see below), whose sum is σ = 995904. Its totient is φ = 432000.

The previous prime is 661373. The next prime is 661393. The reversal of 661375 is 573166.

661375 = 15³ + 16³ + ... + 40³.

It is not a de Polignac number, because 661375 - 2¹ = 661373 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661373) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 17857 + ... + 17893.

It is an arithmetic number, because the mean of its divisors is an integer number (31122).

2⁶⁶¹³⁷⁵ is an apocalyptic number.

661375 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

661375 is the 407-th decagonal number.

661375 is a deficient number, since it is larger than the sum of its proper divisors (334529).

661375 is a wasteful number, since it uses less digits than its factorization.

661375 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 76 (or 66 counting only the distinct ones).

The product of its digits is 3780, while the sum is 28.

The square root of 661375 is about 813.2496541653. The cubic root of 661375 is about 87.1262973870.

Subtracting from 661375 its reverse (573166), we obtain a square (88209 = 297²).

It can be divided in two parts, 66 and 1375, that added together give a palindrome (1441).

The spelling of 661375 in words is "six hundred sixty-one thousand, three hundred seventy-five".