78836721 has 4 divisors (see below), whose sum is σ = 105115632. Its totient is φ = 52557812.

The previous prime is 78836713. The next prime is 78836729. The reversal of 78836721 is 12763887.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12763887 = 3 ⋅4254629.

It is an interprime number because it is at equal distance from previous prime (78836713) and next prime (78836729).

It is a cyclic number.

It is not a de Polignac number, because 78836721 - 2³ = 78836713 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (78836729) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13139451 + ... + 13139456.

It is an arithmetic number, because the mean of its divisors is an integer number (26278908).

Almost surely, 2^78836721 is an apocalyptic number.

It is an amenable number.

78836721 is a deficient number, since it is larger than the sum of its proper divisors (26278911).

78836721 is a wasteful number, since it uses less digits than its factorization.

78836721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26278910.

The product of its digits is 112896, while the sum is 42.

The square root of 78836721 is about 8879.0045050107. The cubic root of 78836721 is about 428.7882252495.

The spelling of 78836721 in words is "seventy-eight million, eight hundred thirty-six thousand, seven hundred twenty-one".