661040161 has 4 divisors (see below), whose sum is σ = 676413232. Its totient is φ = 645667092.

The previous prime is 661040147. The next prime is 661040213. The reversal of 661040161 is 161040166.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 661040161 - 2⁹ = 661039649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661044161) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7686471 + ... + 7686556.

It is an arithmetic number, because the mean of its divisors is an integer number (169103308).

Almost surely, 2^661040161 is an apocalyptic number.

It is an amenable number.

661040161 is a deficient number, since it is larger than the sum of its proper divisors (15373071).

661040161 is a wasteful number, since it uses less digits than its factorization.

661040161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15373070.

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 661040161 is about 25710.7012934303. The cubic root of 661040161 is about 871.1159155600.

The spelling of 661040161 in words is "six hundred sixty-one million, forty thousand, one hundred sixty-one".