19809561 has 8 divisors (see below), whose sum is σ = 26459104. Its totient is φ = 13183200.

The previous prime is 19809557. The next prime is 19809563. The reversal of 19809561 is 16590891.

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

It is not a de Polignac number, because 19809561 - 2² = 19809557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19809563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3691 + ... + 7296.

It is an arithmetic number, because the mean of its divisors is an integer number (3307388).

Almost surely, 2^19809561 is an apocalyptic number.

It is an amenable number.

19809561 is a deficient number, since it is larger than the sum of its proper divisors (6649543).

19809561 is a wasteful number, since it uses less digits than its factorization.

19809561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11591.

The product of its (nonzero) digits is 19440, while the sum is 39.

The square root of 19809561 is about 4450.7933000758. The cubic root of 19809561 is about 270.5774609233.

The spelling of 19809561 in words is "nineteen million, eight hundred nine thousand, five hundred sixty-one".