91821637 has 2 divisors, whose sum is σ = 91821638. Its totient is φ = 91821636.

The previous prime is 91821629. The next prime is 91821643. The reversal of 91821637 is 73612819.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 74632321 + 17189316 = 8639^2 + 4146^2 .

It is a cyclic number.

It is not a de Polignac number, because 91821637 - 2³ = 91821629 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 91821596 and 91821605.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91821677) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45910818 + 45910819.

It is an arithmetic number, because the mean of its divisors is an integer number (45910819).

Almost surely, 2^91821637 is an apocalyptic number.

It is an amenable number.

91821637 is a deficient number, since it is larger than the sum of its proper divisors (1).

91821637 is an equidigital number, since it uses as much as digits as its factorization.

91821637 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18144, while the sum is 37.

The square root of 91821637 is about 9582.3607216594. The cubic root of 91821637 is about 451.1438177331.

The spelling of 91821637 in words is "ninety-one million, eight hundred twenty-one thousand, six hundred thirty-seven".