78721579 has 4 divisors (see below), whose sum is σ = 82864840. Its totient is φ = 74578320.

The previous prime is 78721549. The next prime is 78721597. The reversal of 78721579 is 97512787.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 97512787 = 1009 ⋅96643.

It is a cyclic number.

It is not a de Polignac number, because 78721579 - 2¹³ = 78713387 is a prime.

It is a Duffinian number.

It is a plaindrome in base 12.

It is not an unprimeable number, because it can be changed into a prime (78721529) 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, 2071602 + ... + 2071639.

It is an arithmetic number, because the mean of its divisors is an integer number (20716210).

Almost surely, 2^78721579 is an apocalyptic number.

78721579 is a deficient number, since it is larger than the sum of its proper divisors (4143261).

78721579 is a wasteful number, since it uses less digits than its factorization.

78721579 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4143260.

The product of its digits is 246960, while the sum is 46.

The square root of 78721579 is about 8872.5181882034. The cubic root of 78721579 is about 428.5793733818.

It can be divided in two parts, 787 and 21579, that added together give a triangular number (22366 = T₂₁₁).

The spelling of 78721579 in words is "seventy-eight million, seven hundred twenty-one thousand, five hundred seventy-nine".