561616991 has 16 divisors (see below), whose sum is σ = 648678240. Its totient is φ = 481852800.

The previous prime is 561616963. The next prime is 561617027. The reversal of 561616991 is 199616165.

It is not a de Polignac number, because 561616991 - 2¹⁸ = 561354847 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (561616901) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8360 + ... + 34541.

It is an arithmetic number, because the mean of its divisors is an integer number (40542390).

Almost surely, 2^561616991 is an apocalyptic number.

561616991 is a deficient number, since it is larger than the sum of its proper divisors (87061249).

561616991 is a wasteful number, since it uses less digits than its factorization.

561616991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42986.

The product of its digits is 87480, while the sum is 44.

The square root of 561616991 is about 23698.4596756836. The cubic root of 561616991 is about 825.0496406004.

The spelling of 561616991 in words is "five hundred sixty-one million, six hundred sixteen thousand, nine hundred ninety-one".