78721486921 has 24 divisors (see below), whose sum is σ = 100001018880. Its totient is φ = 60652130880.

The previous prime is 78721486847. The next prime is 78721487023. The reversal of 78721486921 is 12968412787.

It is not a de Polignac number, because 78721486921 - 2¹⁷ = 78721355849 is a prime.

It is not an unprimeable number, because it can be changed into a prime (78721456921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 446761 + ... + 597526.

It is an arithmetic number, because the mean of its divisors is an integer number (4166709120).

Almost surely, 2^78721486921 is an apocalyptic number.

It is an amenable number.

78721486921 is a deficient number, since it is larger than the sum of its proper divisors (21279531959).

78721486921 is a wasteful number, since it uses less digits than its factorization.

78721486921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1044405 (or 1044394 counting only the distinct ones).

The product of its digits is 2709504, while the sum is 55.

The spelling of 78721486921 in words is "seventy-eight billion, seven hundred twenty-one million, four hundred eighty-six thousand, nine hundred twenty-one".