91821053657 has 2 divisors, whose sum is σ = 91821053658. Its totient is φ = 91821053656.

The previous prime is 91821053609. The next prime is 91821053671. The reversal of 91821053657 is 75635012819.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 88988259481 + 2832794176 = 298309^2 + 53224^2 .

It is a cyclic number.

It is not a de Polignac number, because 91821053657 - 2⁶ = 91821053593 is a prime.

It is a super-2 number, since 2×91821053657² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (91821053957) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45910526828 + 45910526829.

It is an arithmetic number, because the mean of its divisors is an integer number (45910526829).

Almost surely, 2^91821053657 is an apocalyptic number.

It is an amenable number.

91821053657 is a deficient number, since it is larger than the sum of its proper divisors (1).

91821053657 is an equidigital number, since it uses as much as digits as its factorization.

91821053657 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 453600, while the sum is 47.

The spelling of 91821053657 in words is "ninety-one billion, eight hundred twenty-one million, fifty-three thousand, six hundred fifty-seven".