78439521 has 4 divisors (see below), whose sum is σ = 104586032. Its totient is φ = 52293012.

The previous prime is 78439489. The next prime is 78439541. The reversal of 78439521 is 12593487.

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: 12593487 = 3 ⋅4197829.

It is not a de Polignac number, because 78439521 - 2⁵ = 78439489 is a prime.

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 78439521.

It is not an unprimeable number, because it can be changed into a prime (78439541) 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, 13073251 + ... + 13073256.

It is an arithmetic number, because the mean of its divisors is an integer number (26146508).

Almost surely, 2^78439521 is an apocalyptic number.

It is an amenable number.

78439521 is a deficient number, since it is larger than the sum of its proper divisors (26146511).

78439521 is a wasteful number, since it uses less digits than its factorization.

78439521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26146510.

The product of its digits is 60480, while the sum is 39.

The square root of 78439521 is about 8856.6088882822. The cubic root of 78439521 is about 428.0668967697.

The spelling of 78439521 in words is "seventy-eight million, four hundred thirty-nine thousand, five hundred twenty-one".