91821139 has 2 divisors, whose sum is σ = 91821140. Its totient is φ = 91821138.

The previous prime is 91821113. The next prime is 91821143. The reversal of 91821139 is 93112819.

It is a strong prime.

It is an emirp because it is prime and its reverse (93112819) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 91821139 - 2⁷ = 91821011 is a prime.

It is a super-2 number, since 2×91821139² = 16862243134514642, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (91821179) 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, 45910569 + 45910570.

It is an arithmetic number, because the mean of its divisors is an integer number (45910570).

Almost surely, 2^91821139 is an apocalyptic number.

91821139 is a deficient number, since it is larger than the sum of its proper divisors (1).

91821139 is an equidigital number, since it uses as much as digits as its factorization.

91821139 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3888, while the sum is 34.

The square root of 91821139 is about 9582.3347363782. The cubic root of 91821139 is about 451.1430021300.

The spelling of 91821139 in words is "ninety-one million, eight hundred twenty-one thousand, one hundred thirty-nine".