91821893 has 2 divisors, whose sum is σ = 91821894. Its totient is φ = 91821892.

The previous prime is 91821869. The next prime is 91821929. The reversal of 91821893 is 39812819.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 50438404 + 41383489 = 7102^2 + 6433^2 .

It is an emirp because it is prime and its reverse (39812819) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 91821893 - 2⁸ = 91821637 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 91821893.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (91821823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45910946 + 45910947.

It is an arithmetic number, because the mean of its divisors is an integer number (45910947).

Almost surely, 2^91821893 is an apocalyptic number.

It is an amenable number.

91821893 is a deficient number, since it is larger than the sum of its proper divisors (1).

91821893 is an equidigital number, since it uses as much as digits as its factorization.

91821893 is an evil number, because the sum of its binary digits is even.

The product of its digits is 31104, while the sum is 41.

The square root of 91821893 is about 9582.3740795275. The cubic root of 91821893 is about 451.1442369978.

The spelling of 91821893 in words is "ninety-one million, eight hundred twenty-one thousand, eight hundred ninety-three".