78138915 has 16 divisors (see below), whose sum is σ = 125424288. Its totient is φ = 41540096.

The previous prime is 78138901. The next prime is 78138917. The reversal of 78138915 is 51983187.

It is a cyclic number.

It is not a de Polignac number, because 78138915 - 2¹¹ = 78136867 is a prime.

It is a super-2 number, since 2×78138915² = 12211380074754450, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (78138917) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3462 + ... + 12971.

It is an arithmetic number, because the mean of its divisors is an integer number (7839018).

Almost surely, 2^78138915 is an apocalyptic number.

78138915 is a deficient number, since it is larger than the sum of its proper divisors (47285373).

78138915 is a wasteful number, since it uses less digits than its factorization.

78138915 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16758.

The product of its digits is 60480, while the sum is 42.

The square root of 78138915 is about 8839.6218810535. The cubic root of 78138915 is about 427.5193657654.

The spelling of 78138915 in words is "seventy-eight million, one hundred thirty-eight thousand, nine hundred fifteen".