78297209 has 4 divisors (see below), whose sum is σ = 78314916. Its totient is φ = 78279504.

The previous prime is 78297181. The next prime is 78297211. The reversal of 78297209 is 90279287.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 44622400 + 33674809 = 6680^2 + 5803^2 .

It is a cyclic number.

It is not a de Polignac number, because 78297209 - 2¹² = 78293113 is a prime.

It is a super-2 number, since 2×78297209² = 12260905874379362, which contains 22 as substring.

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 78297209.

It is not an unprimeable number, because it can be changed into a prime (78297229) 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, 4007 + ... + 13139.

It is an arithmetic number, because the mean of its divisors is an integer number (19578729).

Almost surely, 2^78297209 is an apocalyptic number.

It is an amenable number.

78297209 is a deficient number, since it is larger than the sum of its proper divisors (17707).

78297209 is an equidigital number, since it uses as much as digits as its factorization.

78297209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17706.

The product of its (nonzero) digits is 127008, while the sum is 44.

The square root of 78297209 is about 8848.5710145763. The cubic root of 78297209 is about 427.8078609579.

The spelling of 78297209 in words is "seventy-eight million, two hundred ninety-seven thousand, two hundred nine".