81540213541 has 2 divisors, whose sum is σ = 81540213542. Its totient is φ = 81540213540.

The previous prime is 81540213523. The next prime is 81540213551. The reversal of 81540213541 is 14531204518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 74324390625 + 7215822916 = 272625^2 + 84946^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81540213541 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81540213497 and 81540213506.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81540213551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40770106770 + 40770106771.

It is an arithmetic number, because the mean of its divisors is an integer number (40770106771).

Almost surely, 2^81540213541 is an apocalyptic number.

It is an amenable number.

81540213541 is a deficient number, since it is larger than the sum of its proper divisors (1).

81540213541 is an equidigital number, since it uses as much as digits as its factorization.

81540213541 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 19200, while the sum is 34.

The spelling of 81540213541 in words is "eighty-one billion, five hundred forty million, two hundred thirteen thousand, five hundred forty-one".