661505655 has 32 divisors (see below), whose sum is σ = 1086359040. Its totient is φ = 343601280.

The previous prime is 661505641. The next prime is 661505657. The reversal of 661505655 is 556505166.

It is not a de Polignac number, because 661505655 - 2¹⁰ = 661504631 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661505657) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 90736 + ... + 97754.

It is an arithmetic number, because the mean of its divisors is an integer number (33948720).

Almost surely, 2^661505655 is an apocalyptic number.

661505655 is a deficient number, since it is larger than the sum of its proper divisors (424853385).

661505655 is a wasteful number, since it uses less digits than its factorization.

661505655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7191.

The product of its (nonzero) digits is 135000, while the sum is 39.

The square root of 661505655 is about 25719.7522344209. The cubic root of 661505655 is about 871.3203429212.

The spelling of 661505655 in words is "six hundred sixty-one million, five hundred five thousand, six hundred fifty-five".