78384874921 has 4 divisors (see below), whose sum is σ = 80503385092. Its totient is φ = 76266364752.

The previous prime is 78384874879. The next prime is 78384874957. The reversal of 78384874921 is 12947848387.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 57137731225 + 21247143696 = 239035^2 + 145764^2 .

It is a cyclic number.

It is not a de Polignac number, because 78384874921 - 2¹⁷ = 78384743849 is a prime.

It is a super-2 number, since 2×78384874921² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 78384874921.

It is not an unprimeable number, because it can be changed into a prime (78384874121) 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 3 ways as a sum of consecutive naturals, for example, 1059255030 + ... + 1059255103.

It is an arithmetic number, because the mean of its divisors is an integer number (20125846273).

Almost surely, 2^78384874921 is an apocalyptic number.

It is an amenable number.

78384874921 is a deficient number, since it is larger than the sum of its proper divisors (2118510171).

78384874921 is a wasteful number, since it uses less digits than its factorization.

78384874921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2118510170.

The product of its digits is 21676032, while the sum is 61.

The spelling of 78384874921 in words is "seventy-eight billion, three hundred eighty-four million, eight hundred seventy-four thousand, nine hundred twenty-one".