661560061 has 4 divisors (see below), whose sum is σ = 661636000. Its totient is φ = 661484124.

The previous prime is 661560047. The next prime is 661560071. The reversal of 661560061 is 160065166.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661560061 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661560071) 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, 22911 + ... + 42988.

It is an arithmetic number, because the mean of its divisors is an integer number (165409000).

Almost surely, 2^661560061 is an apocalyptic number.

It is an amenable number.

661560061 is a deficient number, since it is larger than the sum of its proper divisors (75939).

661560061 is a wasteful number, since it uses less digits than its factorization.

661560061 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75938.

The product of its (nonzero) digits is 6480, while the sum is 31.

The square root of 661560061 is about 25720.8098822724. The cubic root of 661560061 is about 871.3442297187.

The spelling of 661560061 in words is "six hundred sixty-one million, five hundred sixty thousand, sixty-one".