81506121353 has 2 divisors, whose sum is σ = 81506121354. Its totient is φ = 81506121352.

The previous prime is 81506121331. The next prime is 81506121371. The reversal of 81506121353 is 35312160518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 62836451584 + 18669669769 = 250672^2 + 136637^2 .

It is a cyclic number.

It is not a de Polignac number, because 81506121353 - 2¹⁸ = 81505859209 is a prime.

It is not a weakly prime, because it can be changed into another prime (81506121373) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40753060676 + 40753060677.

It is an arithmetic number, because the mean of its divisors is an integer number (40753060677).

Almost surely, 2^81506121353 is an apocalyptic number.

It is an amenable number.

81506121353 is a deficient number, since it is larger than the sum of its proper divisors (1).

81506121353 is an equidigital number, since it uses as much as digits as its factorization.

81506121353 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 21600, while the sum is 35.

The spelling of 81506121353 in words is "eighty-one billion, five hundred six million, one hundred twenty-one thousand, three hundred fifty-three".