78121801 has 4 divisors (see below), whose sum is σ = 78140052. Its totient is φ = 78103552.

The previous prime is 78121793. The next prime is 78121811. The reversal of 78121801 is 10812187.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 22231225 + 55890576 = 4715^2 + 7476^2 .

It is a cyclic number.

It is not a de Polignac number, because 78121801 - 2³ = 78121793 is a prime.

It is a super-2 number, since 2×78121801² = 12206031582967202, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 78121801.

It is not an unprimeable number, because it can be changed into a prime (78121811) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1161 + ... + 12553.

It is an arithmetic number, because the mean of its divisors is an integer number (19535013).

Almost surely, 2^78121801 is an apocalyptic number.

It is an amenable number.

78121801 is a deficient number, since it is larger than the sum of its proper divisors (18251).

78121801 is a wasteful number, since it uses less digits than its factorization.

78121801 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18250.

The product of its (nonzero) digits is 896, while the sum is 28.

The square root of 78121801 is about 8838.6538002119. The cubic root of 78121801 is about 427.4881516956.

Adding to 78121801 its reverse (10812187), we get a palindrome (88933988).

The spelling of 78121801 in words is "seventy-eight million, one hundred twenty-one thousand, eight hundred one".