91636778 has 4 divisors (see below), whose sum is σ = 137455170. Its totient is φ = 45818388.

The previous prime is 91636777. The next prime is 91636799. The reversal of 91636778 is 87763619.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 87763619 = 83 ⋅1057393.

It can be written as a sum of positive squares in only one way, i.e., 74356129 + 17280649 = 8623^2 + 4157^2 .

It is not an unprimeable number, because it can be changed into a prime (91636777) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 22909193 + ... + 22909196.

Almost surely, 2^91636778 is an apocalyptic number.

91636778 is a deficient number, since it is larger than the sum of its proper divisors (45818392).

91636778 is a wasteful number, since it uses less digits than its factorization.

91636778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45818391.

The product of its digits is 381024, while the sum is 47.

The square root of 91636778 is about 9572.7100655979. The cubic root of 91636778 is about 450.8408607281.

The spelling of 91636778 in words is "ninety-one million, six hundred thirty-six thousand, seven hundred seventy-eight".