818794780721 has 2 divisors, whose sum is σ = 818794780722. Its totient is φ = 818794780720.

The previous prime is 818794780693. The next prime is 818794780777. The reversal of 818794780721 is 127087497818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 738334621696 + 80460159025 = 859264^2 + 283655^2 .

It is a cyclic number.

It is not a de Polignac number, because 818794780721 - 2²⁶ = 818727671857 is a prime.

It is not a weakly prime, because it can be changed into another prime (818794780021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 409397390360 + 409397390361.

It is an arithmetic number, because the mean of its divisors is an integer number (409397390361).

Almost surely, 2^818794780721 is an apocalyptic number.

It is an amenable number.

818794780721 is a deficient number, since it is larger than the sum of its proper divisors (1).

818794780721 is an equidigital number, since it uses as much as digits as its factorization.

818794780721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12644352, while the sum is 62.

The spelling of 818794780721 in words is "eight hundred eighteen billion, seven hundred ninety-four million, seven hundred eighty thousand, seven hundred twenty-one".