661161561 has 8 divisors (see below), whose sum is σ = 894706464. Its totient is φ = 434195520.

The previous prime is 661161559. The next prime is 661161581. The reversal of 661161561 is 165161166.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 661161561 - 2¹ = 661161559 is a prime.

It is not an unprimeable number, because it can be changed into a prime (661161581) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1644480 + ... + 1644881.

It is an arithmetic number, because the mean of its divisors is an integer number (111838308).

Almost surely, 2^661161561 is an apocalyptic number.

It is an amenable number.

661161561 is a deficient number, since it is larger than the sum of its proper divisors (233544903).

661161561 is a wasteful number, since it uses less digits than its factorization.

661161561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3289431.

The product of its digits is 6480, while the sum is 33.

The square root of 661161561 is about 25713.0620696952. The cubic root of 661161561 is about 871.1692390973.

The spelling of 661161561 in words is "six hundred sixty-one million, one hundred sixty-one thousand, five hundred sixty-one".