661705549 has 2 divisors, whose sum is σ = 661705550. Its totient is φ = 661705548.

The previous prime is 661705489. The next prime is 661705559. The reversal of 661705549 is 945507166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 589761225 + 71944324 = 24285^2 + 8482^2 .

It is a cyclic number.

It is not a de Polignac number, because 661705549 - 2¹³ = 661697357 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661705559) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330852774 + 330852775.

It is an arithmetic number, because the mean of its divisors is an integer number (330852775).

Almost surely, 2^661705549 is an apocalyptic number.

It is an amenable number.

661705549 is a deficient number, since it is larger than the sum of its proper divisors (1).

661705549 is an equidigital number, since it uses as much as digits as its factorization.

661705549 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 226800, while the sum is 43.

The square root of 661705549 is about 25723.6379425617. The cubic root of 661705549 is about 871.4080993732.

The spelling of 661705549 in words is "six hundred sixty-one million, seven hundred five thousand, five hundred forty-nine".