78525509 has 4 divisors (see below), whose sum is σ = 78609900. Its totient is φ = 78441120.

The previous prime is 78525493. The next prime is 78525521. The reversal of 78525509 is 90552587.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 26368225 + 52157284 = 5135^2 + 7222^2 .

It is a cyclic number.

It is not a de Polignac number, because 78525509 - 2⁴ = 78525493 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78525529) 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, 40784 + ... + 42665.

It is an arithmetic number, because the mean of its divisors is an integer number (19652475).

Almost surely, 2^78525509 is an apocalyptic number.

It is an amenable number.

78525509 is a deficient number, since it is larger than the sum of its proper divisors (84391).

78525509 is an equidigital number, since it uses as much as digits as its factorization.

78525509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84390.

The product of its (nonzero) digits is 126000, while the sum is 41.

The square root of 78525509 is about 8861.4620125575. The cubic root of 78525509 is about 428.2232600152.

The spelling of 78525509 in words is "seventy-eight million, five hundred twenty-five thousand, five hundred nine".