661155577 has 4 divisors (see below), whose sum is σ = 661207140. Its totient is φ = 661104016.

The previous prime is 661155571. The next prime is 661155613. The reversal of 661155577 is 775551166.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 17214201 + 643941376 = 4149^2 + 25376^2 .

It is a cyclic number.

It is not a de Polignac number, because 661155577 - 2¹¹ = 661153529 is a prime.

It is a Duffinian number.

It is a zygodrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (661155571) 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, 10083 + ... + 37735.

It is an arithmetic number, because the mean of its divisors is an integer number (165301785).

Almost surely, 2^661155577 is an apocalyptic number.

It is an amenable number.

661155577 is a deficient number, since it is larger than the sum of its proper divisors (51563).

661155577 is a wasteful number, since it uses less digits than its factorization.

661155577 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51562.

The product of its digits is 220500, while the sum is 43.

The square root of 661155577 is about 25712.9457083392. The cubic root of 661155577 is about 871.1666108478.

The spelling of 661155577 in words is "six hundred sixty-one million, one hundred fifty-five thousand, five hundred seventy-seven".