91378494561 has 4 divisors (see below), whose sum is σ = 121837992752. Its totient is φ = 60918996372.

The previous prime is 91378494553. The next prime is 91378494577. The reversal of 91378494561 is 16549487319.

It is a happy number.

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: 16549487319 = 3 ⋅5516495773.

It is not a de Polignac number, because 91378494561 - 2³ = 91378494553 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (91378494551) 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, 15229749091 + ... + 15229749096.

It is an arithmetic number, because the mean of its divisors is an integer number (30459498188).

Almost surely, 2^91378494561 is an apocalyptic number.

It is an amenable number.

91378494561 is a deficient number, since it is larger than the sum of its proper divisors (30459498191).

91378494561 is a wasteful number, since it uses less digits than its factorization.

91378494561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30459498190.

The product of its digits is 6531840, while the sum is 57.

The spelling of 91378494561 in words is "ninety-one billion, three hundred seventy-eight million, four hundred ninety-four thousand, five hundred sixty-one".