1561835661 has 8 divisors (see below), whose sum is σ = 2088123264. Its totient is φ = 1038385920.

The previous prime is 1561835633. The next prime is 1561835683. The reversal of 1561835661 is 1665381651.

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

It is not a de Polignac number, because 1561835661 - 2⁷ = 1561835533 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561835161) 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 7 ways as a sum of consecutive naturals, for example, 708180 + ... + 710381.

It is an arithmetic number, because the mean of its divisors is an integer number (261015408).

Almost surely, 2^1561835661 is an apocalyptic number.

It is an amenable number.

1561835661 is a deficient number, since it is larger than the sum of its proper divisors (526287603).

1561835661 is a wasteful number, since it uses less digits than its factorization.

1561835661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1418931.

The product of its digits is 129600, while the sum is 42.

The square root of 1561835661 is about 39520.0665611788. The cubic root of 1561835661 is about 1160.2327270373.

The spelling of 1561835661 in words is "one billion, five hundred sixty-one million, eight hundred thirty-five thousand, six hundred sixty-one".