91778289 has 4 divisors (see below), whose sum is σ = 122371056. Its totient is φ = 61185524.

The previous prime is 91778279. The next prime is 91778293. The reversal of 91778289 is 98287719.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 98287719 = 3 ⋅32762573.

It is a cyclic number.

It is not a de Polignac number, because 91778289 - 2¹⁹ = 91254001 is a prime.

It is not an unprimeable number, because it can be changed into a prime (91778209) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15296379 + ... + 15296384.

It is an arithmetic number, because the mean of its divisors is an integer number (30592764).

Almost surely, 2^91778289 is an apocalyptic number.

It is an amenable number.

91778289 is a deficient number, since it is larger than the sum of its proper divisors (30592767).

91778289 is a wasteful number, since it uses less digits than its factorization.

91778289 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30592766.

The product of its digits is 508032, while the sum is 51.

The square root of 91778289 is about 9580.0985903069. The cubic root of 91778289 is about 451.0728131889.

The spelling of 91778289 in words is "ninety-one million, seven hundred seventy-eight thousand, two hundred eighty-nine".