81250501721 has 2 divisors, whose sum is σ = 81250501722. Its totient is φ = 81250501720.

The previous prime is 81250501699. The next prime is 81250501751. The reversal of 81250501721 is 12710505218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 50562469321 + 30688032400 = 224861^2 + 175180^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81250501721 is a prime.

It is not a weakly prime, because it can be changed into another prime (81250501751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40625250860 + 40625250861.

It is an arithmetic number, because the mean of its divisors is an integer number (40625250861).

Almost surely, 2^81250501721 is an apocalyptic number.

It is an amenable number.

81250501721 is a deficient number, since it is larger than the sum of its proper divisors (1).

81250501721 is an equidigital number, since it uses as much as digits as its factorization.

81250501721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5600, while the sum is 32.

The spelling of 81250501721 in words is "eighty-one billion, two hundred fifty million, five hundred one thousand, seven hundred twenty-one".