661157865 has 12 divisors (see below), whose sum is σ = 1146007044. Its totient is φ = 352617504.

The previous prime is 661157851. The next prime is 661157867. The reversal of 661157865 is 568751166.

661157865 is a `hidden beast` number, since 6 + 6 + 11 + 578 + 65 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 326597184 + 334560681 = 18072^2 + 18291^2 .

It is not a de Polignac number, because 661157865 - 2⁷ = 661157737 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 14692397 = 661157865 / (6 + 6 + 1 + 1 + 5 + 7 + 8 + 6 + 5).

It is a self number, because there is not a number n which added to its sum of digits gives 661157865.

It is not an unprimeable number, because it can be changed into a prime (661157867) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7346154 + ... + 7346243.

It is an arithmetic number, because the mean of its divisors is an integer number (95500587).

Almost surely, 2^661157865 is an apocalyptic number.

It is an amenable number.

661157865 is a deficient number, since it is larger than the sum of its proper divisors (484849179).

661157865 is a wasteful number, since it uses less digits than its factorization.

661157865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14692408 (or 14692405 counting only the distinct ones).

The product of its digits is 302400, while the sum is 45.

The square root of 661157865 is about 25712.9901995081. The cubic root of 661157865 is about 871.1676157686.

The spelling of 661157865 in words is "six hundred sixty-one million, one hundred fifty-seven thousand, eight hundred sixty-five".