81077313221 has 2 divisors, whose sum is σ = 81077313222. Its totient is φ = 81077313220.

The previous prime is 81077313167. The next prime is 81077313277. The reversal of 81077313221 is 12231377018.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81056937025 + 20376196 = 284705^2 + 4514^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81077313221 is a prime.

It is a super-2 number, since 2×81077313221² (a number of 23 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81077313721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40538656610 + 40538656611.

It is an arithmetic number, because the mean of its divisors is an integer number (40538656611).

Almost surely, 2^81077313221 is an apocalyptic number.

It is an amenable number.

81077313221 is a deficient number, since it is larger than the sum of its proper divisors (1).

81077313221 is an equidigital number, since it uses as much as digits as its factorization.

81077313221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 14112, while the sum is 35.

The spelling of 81077313221 in words is "eighty-one billion, seventy-seven million, three hundred thirteen thousand, two hundred twenty-one".