78997721746 has 4 divisors (see below), whose sum is σ = 118496582622. Its totient is φ = 39498860872.

The previous prime is 78997721731. The next prime is 78997721749. The reversal of 78997721746 is 64712779987.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 64712779987 = 1231 ⋅52569277.

It can be written as a sum of positive squares in only one way, i.e., 70788455721 + 8209266025 = 266061^2 + 90605^2 .

It is a Smith number, since the sum of its digits (67) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (78997721749) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 19749430435 + ... + 19749430438.

Almost surely, 2^78997721746 is an apocalyptic number.

78997721746 is a deficient number, since it is larger than the sum of its proper divisors (39498860876).

78997721746 is a wasteful number, since it uses less digits than its factorization.

78997721746 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39498860875.

The product of its digits is 74680704, while the sum is 67.

The spelling of 78997721746 in words is "seventy-eight billion, nine hundred ninety-seven million, seven hundred twenty-one thousand, seven hundred forty-six".