611661561 has 24 divisors (see below), whose sum is σ = 949977504. Its totient is φ = 349050240.

The previous prime is 611661511. The next prime is 611661569. The reversal of 611661561 is 165166116.

It is not a de Polignac number, because 611661561 - 2⁶ = 611661497 is a prime.

It is not an unprimeable number, because it can be changed into a prime (611661569) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 127146 + ... + 131868.

It is an arithmetic number, because the mean of its divisors is an integer number (39582396).

Almost surely, 2^611661561 is an apocalyptic number.

It is an amenable number.

611661561 is a deficient number, since it is larger than the sum of its proper divisors (338315943).

611661561 is a wasteful number, since it uses less digits than its factorization.

611661561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5621 (or 5614 counting only the distinct ones).

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

The square root of 611661561 is about 24731.7925148987. The cubic root of 611661561 is about 848.8619422267.

The spelling of 611661561 in words is "six hundred eleven million, six hundred sixty-one thousand, five hundred sixty-one".