661545 has 24 divisors (see below), whose sum is σ = 1170312. Its totient is φ = 345600.

The previous prime is 661541. The next prime is 661547. The reversal of 661545 is 545166.

It is a happy number.

661545 is a `hidden beast` number, since 6 + 615 + 45 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 15129 + 646416 = 123^2 + 804^2 .

It is not a de Polignac number, because 661545 - 2² = 661541 is a prime.

It is not an unprimeable number, because it can be changed into a prime (661541) 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 23 ways as a sum of consecutive naturals, for example, 2625 + ... + 2865.

It is an arithmetic number, because the mean of its divisors is an integer number (48763).

2⁶⁶¹⁵⁴⁵ is an apocalyptic number.

It is an amenable number.

661545 is a deficient number, since it is larger than the sum of its proper divisors (508767).

661545 is a wasteful number, since it uses less digits than its factorization.

661545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 313 (or 310 counting only the distinct ones).

The product of its digits is 3600, while the sum is 27.

The square root of 661545 is about 813.3541663999. The cubic root of 661545 is about 87.1337617361.

The spelling of 661545 in words is "six hundred sixty-one thousand, five hundred forty-five".