81026761021 has 2 divisors, whose sum is σ = 81026761022. Its totient is φ = 81026761020.

The previous prime is 81026760943. The next prime is 81026761177. The reversal of 81026761021 is 12016762018.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 55622864025 + 25403896996 = 235845^2 + 159386^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81026761021 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81026761421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40513380510 + 40513380511.

It is an arithmetic number, because the mean of its divisors is an integer number (40513380511).

Almost surely, 2^81026761021 is an apocalyptic number.

It is an amenable number.

81026761021 is a deficient number, since it is larger than the sum of its proper divisors (1).

81026761021 is an equidigital number, since it uses as much as digits as its factorization.

81026761021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8064, while the sum is 34.

The spelling of 81026761021 in words is "eighty-one billion, twenty-six million, seven hundred sixty-one thousand, twenty-one".