81900313657 has 2 divisors, whose sum is σ = 81900313658. Its totient is φ = 81900313656.

The previous prime is 81900313609. The next prime is 81900313699. The reversal of 81900313657 is 75631300918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 76339479616 + 5560834041 = 276296^2 + 74571^2 .

It is a cyclic number.

It is not a de Polignac number, because 81900313657 - 2³¹ = 79752830009 is a prime.

It is a super-2 number, since 2×81900313657² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81900313357) 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, 40950156828 + 40950156829.

It is an arithmetic number, because the mean of its divisors is an integer number (40950156829).

Almost surely, 2^81900313657 is an apocalyptic number.

It is an amenable number.

81900313657 is a deficient number, since it is larger than the sum of its proper divisors (1).

81900313657 is an equidigital number, since it uses as much as digits as its factorization.

81900313657 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 136080, while the sum is 43.

The spelling of 81900313657 in words is "eighty-one billion, nine hundred million, three hundred thirteen thousand, six hundred fifty-seven".