81551821897753 has 2 divisors, whose sum is σ = 81551821897754. Its totient is φ = 81551821897752.

The previous prime is 81551821897613. The next prime is 81551821897759. The reversal of 81551821897753 is 35779812815518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 60014723004889 + 21537098892864 = 7746917^2 + 4640808^2 .

It is a cyclic number.

It is not a de Polignac number, because 81551821897753 - 2¹³ = 81551821889561 is a prime.

It is not a weakly prime, because it can be changed into another prime (81551821897759) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40775910948876 + 40775910948877.

It is an arithmetic number, because the mean of its divisors is an integer number (40775910948877).

Almost surely, 2^{81551821897753} is an apocalyptic number.

It is an amenable number.

81551821897753 is a deficient number, since it is larger than the sum of its proper divisors (1).

81551821897753 is an equidigital number, since it uses as much as digits as its factorization.

81551821897753 is an evil number, because the sum of its binary digits is even.

The product of its digits is 169344000, while the sum is 70.

The spelling of 81551821897753 in words is "eighty-one trillion, five hundred fifty-one billion, eight hundred twenty-one million, eight hundred ninety-seven thousand, seven hundred fifty-three".