1561446991 has 8 divisors (see below), whose sum is σ = 1780473744. Its totient is φ = 1356551040.

The previous prime is 1561446979. The next prime is 1561447009. The reversal of 1561446991 is 1996441651.

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

It is not a de Polignac number, because 1561446991 - 2⁷ = 1561446863 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 (1561446941) 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, 3532465 + ... + 3532906.

It is an arithmetic number, because the mean of its divisors is an integer number (222559218).

Almost surely, 2^1561446991 is an apocalyptic number.

1561446991 is a deficient number, since it is larger than the sum of its proper divisors (219026753).

1561446991 is a wasteful number, since it uses less digits than its factorization.

1561446991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7065401.

The product of its digits is 233280, while the sum is 46.

The square root of 1561446991 is about 39515.1488798916. The cubic root of 1561446991 is about 1160.1364759661.

The spelling of 1561446991 in words is "one billion, five hundred sixty-one million, four hundred forty-six thousand, nine hundred ninety-one".