78215791 has 2 divisors, whose sum is σ = 78215792. Its totient is φ = 78215790.

The previous prime is 78215789. The next prime is 78215833. The reversal of 78215791 is 19751287.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 78215791 - 2¹ = 78215789 is a prime.

It is a super-2 number, since 2×78215791² = 12235419923511362, which contains 22 as substring.

Together with 78215789, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78215701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39107895 + 39107896.

It is an arithmetic number, because the mean of its divisors is an integer number (39107896).

Almost surely, 2^78215791 is an apocalyptic number.

78215791 is a deficient number, since it is larger than the sum of its proper divisors (1).

78215791 is an equidigital number, since it uses as much as digits as its factorization.

78215791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 35280, while the sum is 40.

The square root of 78215791 is about 8843.9691880965. The cubic root of 78215791 is about 427.6595230157.

The spelling of 78215791 in words is "seventy-eight million, two hundred fifteen thousand, seven hundred ninety-one".