78288521 has 4 divisors (see below), whose sum is σ = 78787332. Its totient is φ = 77789712.

The previous prime is 78288503. The next prime is 78288523. The reversal of 78288521 is 12588287.

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 49505296 + 28783225 = 7036^2 + 5365^2 .

It is a cyclic number.

It is not a de Polignac number, because 78288521 - 2¹⁰ = 78287497 is a prime.

It is a super-2 number, since 2×78288521² = 12258185040734882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78288523) 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, 249170 + ... + 249483.

It is an arithmetic number, because the mean of its divisors is an integer number (19696833).

Almost surely, 2^78288521 is an apocalyptic number.

It is an amenable number.

78288521 is a deficient number, since it is larger than the sum of its proper divisors (498811).

78288521 is a wasteful number, since it uses less digits than its factorization.

78288521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 498810.

The product of its digits is 71680, while the sum is 41.

The square root of 78288521 is about 8848.0800742308. The cubic root of 78288521 is about 427.7920369278.

The spelling of 78288521 in words is "seventy-eight million, two hundred eighty-eight thousand, five hundred twenty-one".