19978744691 has 8 divisors (see below), whose sum is σ = 20402094240. Its totient is φ = 19557113472.

The previous prime is 19978744637. The next prime is 19978744711. The reversal of 19978744691 is 19644787991.

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 19978744691 - 2³⁴ = 2798875507 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19978744601) 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, 406070 + ... + 452603.

It is an arithmetic number, because the mean of its divisors is an integer number (2550261780).

Almost surely, 2^19978744691 is an apocalyptic number.

19978744691 is a deficient number, since it is larger than the sum of its proper divisors (423349549).

19978744691 is an equidigital number, since it uses as much as digits as its factorization.

19978744691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 859165.

The product of its digits is 27433728, while the sum is 65.

The spelling of 19978744691 in words is "nineteen billion, nine hundred seventy-eight million, seven hundred forty-four thousand, six hundred ninety-one".