661201331665 has 64 divisors (see below), whose sum is σ = 958757437440. Its totient is φ = 428141790720.

The previous prime is 661201331647. The next prime is 661201331671. The reversal of 661201331665 is 566133102166.

It is not a de Polignac number, because 661201331665 - 2²¹ = 661199234513 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 51174076 + ... + 51186994.

It is an arithmetic number, because the mean of its divisors is an integer number (14980584960).

Almost surely, 2^661201331665 is an apocalyptic number.

It is an amenable number.

661201331665 is a deficient number, since it is larger than the sum of its proper divisors (297556105775).

661201331665 is a wasteful number, since it uses less digits than its factorization.

661201331665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14102.

The product of its (nonzero) digits is 116640, while the sum is 40.

The spelling of 661201331665 in words is "six hundred sixty-one billion, two hundred one million, three hundred thirty-one thousand, six hundred sixty-five".