81500521 has 2 divisors, whose sum is σ = 81500522. Its totient is φ = 81500520.

The previous prime is 81500513. The next prime is 81500561. The reversal of 81500521 is 12500518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 75429225 + 6071296 = 8685^2 + 2464^2 .

It is a cyclic number.

It is not a de Polignac number, because 81500521 - 2³ = 81500513 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81500492 and 81500501.

It is not a weakly prime, because it can be changed into another prime (81500561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40750260 + 40750261.

It is an arithmetic number, because the mean of its divisors is an integer number (40750261).

Almost surely, 2^81500521 is an apocalyptic number.

It is an amenable number.

81500521 is a deficient number, since it is larger than the sum of its proper divisors (1).

81500521 is an equidigital number, since it uses as much as digits as its factorization.

81500521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 400, while the sum is 22.

The square root of 81500521 is about 9027.7638981090. The cubic root of 81500521 is about 433.5642468835.

The spelling of 81500521 in words is "eighty-one million, five hundred thousand, five hundred twenty-one".