78121819 has 2 divisors, whose sum is σ = 78121820. Its totient is φ = 78121818.

The previous prime is 78121811. The next prime is 78121843. The reversal of 78121819 is 91812187.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 78121819 - 2³ = 78121811 is a prime.

It is a super-2 number, since 2×78121819² = 12206037207737522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (78121811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39060909 + 39060910.

It is an arithmetic number, because the mean of its divisors is an integer number (39060910).

Almost surely, 2^78121819 is an apocalyptic number.

78121819 is a deficient number, since it is larger than the sum of its proper divisors (1).

78121819 is an equidigital number, since it uses as much as digits as its factorization.

78121819 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8064, while the sum is 37.

The square root of 78121819 is about 8838.6548184664. The cubic root of 78121819 is about 427.4881845280.

The spelling of 78121819 in words is "seventy-eight million, one hundred twenty-one thousand, eight hundred nineteen".