78121013 has 2 divisors, whose sum is σ = 78121014. Its totient is φ = 78121012.

The previous prime is 78121009. The next prime is 78121039. The reversal of 78121013 is 31012187.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 51008164 + 27112849 = 7142^2 + 5207^2 .

It is an emirp because it is prime and its reverse (31012187) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 78121013 - 2² = 78121009 is a prime.

It is a super-3 number, since 3×78121013³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a self number, because there is not a number n which added to its sum of digits gives 78121013.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78121073) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39060506 + 39060507.

It is an arithmetic number, because the mean of its divisors is an integer number (39060507).

Almost surely, 2^78121013 is an apocalyptic number.

It is an amenable number.

78121013 is a deficient number, since it is larger than the sum of its proper divisors (1).

78121013 is an equidigital number, since it uses as much as digits as its factorization.

78121013 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 336, while the sum is 23.

The square root of 78121013 is about 8838.6092231753. The cubic root of 78121013 is about 427.4867143598.

The spelling of 78121013 in words is "seventy-eight million, one hundred twenty-one thousand, thirteen".