91821643 has 2 divisors, whose sum is σ = 91821644. Its totient is φ = 91821642.

The previous prime is 91821637. The next prime is 91821677. The reversal of 91821643 is 34612819.

It is an a-pointer prime, because the next prime (91821677) can be obtained adding 91821643 to its sum of digits (34).

It is a weak prime.

It is an emirp because it is prime and its reverse (34612819) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 91821643 - 2¹³ = 91813451 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 91821599 and 91821608.

It is not a weakly prime, because it can be changed into another prime (91821683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45910821 + 45910822.

It is an arithmetic number, because the mean of its divisors is an integer number (45910822).

Almost surely, 2^91821643 is an apocalyptic number.

91821643 is a deficient number, since it is larger than the sum of its proper divisors (1).

91821643 is an equidigital number, since it uses as much as digits as its factorization.

91821643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10368, while the sum is 34.

The square root of 91821643 is about 9582.3610347346. The cubic root of 91821643 is about 451.1438275596.

The spelling of 91821643 in words is "ninety-one million, eight hundred twenty-one thousand, six hundred forty-three".