19999012561 has 8 divisors (see below), whose sum is σ = 22406756544. Its totient is φ = 17689543920.

The previous prime is 19999012549. The next prime is 19999012637. The reversal of 19999012561 is 16521099991.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 19999012561 - 2⁵ = 19999012529 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 19999012499 and 19999012508.

It is not an unprimeable number, because it can be changed into a prime (19999012531) 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, 24568405 + ... + 24569218.

It is an arithmetic number, because the mean of its divisors is an integer number (2800844568).

Almost surely, 2^19999012561 is an apocalyptic number.

19999012561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

19999012561 is a deficient number, since it is larger than the sum of its proper divisors (2407743983).

19999012561 is a wasteful number, since it uses less digits than its factorization.

19999012561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49137671.

The product of its (nonzero) digits is 393660, while the sum is 52.

The spelling of 19999012561 in words is "nineteen billion, nine hundred ninety-nine million, twelve thousand, five hundred sixty-one".