81890789621761 has 2 divisors, whose sum is σ = 81890789621762. Its totient is φ = 81890789621760.

The previous prime is 81890789621731. The next prime is 81890789621833. The reversal of 81890789621761 is 16712698709818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81398631250161 + 492158371600 = 9022119^2 + 701540^2 .

It is a cyclic number.

It is not a de Polignac number, because 81890789621761 - 2¹⁷ = 81890789490689 is a prime.

It is a super-2 number, since 2×81890789621761² (a number of 29 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81890789621731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40945394810880 + 40945394810881.

It is an arithmetic number, because the mean of its divisors is an integer number (40945394810881).

Almost surely, 2^{81890789621761} is an apocalyptic number.

It is an amenable number.

81890789621761 is a deficient number, since it is larger than the sum of its proper divisors (1).

81890789621761 is an equidigital number, since it uses as much as digits as its factorization.

81890789621761 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 146313216, while the sum is 73.

The spelling of 81890789621761 in words is "eighty-one trillion, eight hundred ninety billion, seven hundred eighty-nine million, six hundred twenty-one thousand, seven hundred sixty-one".