78406609 has 4 divisors (see below), whose sum is σ = 81815616. Its totient is φ = 74997604.

The previous prime is 78406583. The next prime is 78406621. The reversal of 78406609 is 90660487.

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: 90660487 = 8011 ⋅11317.

It is a cyclic number.

It is not a de Polignac number, because 78406609 - 2¹⁷ = 78275537 is a prime.

It is a super-2 number, since 2×78406609² = 12295192669757762, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78406639) 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, 1704469 + ... + 1704514.

It is an arithmetic number, because the mean of its divisors is an integer number (20453904).

Almost surely, 2^78406609 is an apocalyptic number.

It is an amenable number.

78406609 is a deficient number, since it is larger than the sum of its proper divisors (3409007).

78406609 is a wasteful number, since it uses less digits than its factorization.

78406609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3409006.

The product of its (nonzero) digits is 72576, while the sum is 40.

The square root of 78406609 is about 8854.7506458398. The cubic root of 78406609 is about 428.0070183290.

The spelling of 78406609 in words is "seventy-eight million, four hundred six thousand, six hundred nine".