19721756847 has 16 divisors (see below), whose sum is σ = 29549657088. Its totient is φ = 11608792800.

The previous prime is 19721756843. The next prime is 19721756881. The reversal of 19721756847 is 74865712791.

It is not a de Polignac number, because 19721756847 - 2² = 19721756843 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19721756843) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10992279 + ... + 10994072.

It is an arithmetic number, because the mean of its divisors is an integer number (1846853568).

Almost surely, 2^19721756847 is an apocalyptic number.

19721756847 is a deficient number, since it is larger than the sum of its proper divisors (9827900241).

19721756847 is a wasteful number, since it uses less digits than its factorization.

19721756847 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21986390.

The product of its digits is 5927040, while the sum is 57.

The spelling of 19721756847 in words is "nineteen billion, seven hundred twenty-one million, seven hundred fifty-six thousand, eight hundred forty-seven".