78378991 has 2 divisors, whose sum is σ = 78378992. Its totient is φ = 78378990.

The previous prime is 78378941. The next prime is 78379013. The reversal of 78378991 is 19987387.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 78378991 - 2¹⁷ = 78247919 is a prime.

It is a super-2 number, since 2×78378991² = 12286532460356162, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78378901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39189495 + 39189496.

It is an arithmetic number, because the mean of its divisors is an integer number (39189496).

Almost surely, 2^78378991 is an apocalyptic number.

78378991 is a deficient number, since it is larger than the sum of its proper divisors (1).

78378991 is an equidigital number, since it uses as much as digits as its factorization.

78378991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 762048, while the sum is 52.

The square root of 78378991 is about 8853.1910066371. The cubic root of 78378991 is about 427.9567585947.

The spelling of 78378991 in words is "seventy-eight million, three hundred seventy-eight thousand, nine hundred ninety-one".