661541 has 2 divisors, whose sum is σ = 661542. Its totient is φ = 661540.

The previous prime is 661517. The next prime is 661547. The reversal of 661541 is 145166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 568516 + 93025 = 754^2 + 305^2 .

It is a cyclic number.

It is not a de Polignac number, because 661541 - 2⁶ = 661477 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661547) 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 as a sum of consecutive naturals, namely, 330770 + 330771.

It is an arithmetic number, because the mean of its divisors is an integer number (330771).

2⁶⁶¹⁵⁴¹ is an apocalyptic number.

It is an amenable number.

661541 is a deficient number, since it is larger than the sum of its proper divisors (1).

661541 is an equidigital number, since it uses as much as digits as its factorization.

661541 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 720, while the sum is 23.

The square root of 661541 is about 813.3517074427. The cubic root of 661541 is about 87.1335861191.

The spelling of 661541 in words is "six hundred sixty-one thousand, five hundred forty-one".