78668521 has 4 divisors (see below), whose sum is σ = 78891732. Its totient is φ = 78445312.

The previous prime is 78668509. The next prime is 78668563. The reversal of 78668521 is 12586687.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12586687 = 67 ⋅187861.

It can be written as a sum of positive squares in 2 ways, for example, as 35569296 + 43099225 = 5964^2 + 6565^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-78668521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78668591) 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, 111076 + ... + 111781.

It is an arithmetic number, because the mean of its divisors is an integer number (19722933).

Almost surely, 2^78668521 is an apocalyptic number.

It is an amenable number.

78668521 is a deficient number, since it is larger than the sum of its proper divisors (223211).

78668521 is a wasteful number, since it uses less digits than its factorization.

78668521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 223210.

The product of its digits is 161280, while the sum is 43.

The square root of 78668521 is about 8869.5276649887. The cubic root of 78668521 is about 428.4830648669.

The spelling of 78668521 in words is "seventy-eight million, six hundred sixty-eight thousand, five hundred twenty-one".