78278891 has 2 divisors, whose sum is σ = 78278892. Its totient is φ = 78278890.

The previous prime is 78278887. The next prime is 78278909. The reversal of 78278891 is 19887287.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 78278891 - 2² = 78278887 is a prime.

It is a super-2 number, since 2×78278891² = 12255169552379762, which contains 22 as substring.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (78278861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39139445 + 39139446.

It is an arithmetic number, because the mean of its divisors is an integer number (39139446).

Almost surely, 2^78278891 is an apocalyptic number.

78278891 is a deficient number, since it is larger than the sum of its proper divisors (1).

78278891 is an equidigital number, since it uses as much as digits as its factorization.

78278891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 451584, while the sum is 50.

The square root of 78278891 is about 8847.5358716425. The cubic root of 78278891 is about 427.7744958026.

The spelling of 78278891 in words is "seventy-eight million, two hundred seventy-eight thousand, eight hundred ninety-one".