91218993 has 4 divisors (see below), whose sum is σ = 121625328. Its totient is φ = 60812660.

The previous prime is 91218983. The next prime is 91219001. The reversal of 91218993 is 39981219.

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.

It is a cyclic number.

It is not a de Polignac number, because 91218993 - 2⁴ = 91218977 is a prime.

It is not an unprimeable number, because it can be changed into a prime (91218913) 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, 15203163 + ... + 15203168.

It is an arithmetic number, because the mean of its divisors is an integer number (30406332).

Almost surely, 2^91218993 is an apocalyptic number.

It is an amenable number.

91218993 is a deficient number, since it is larger than the sum of its proper divisors (30406335).

91218993 is a wasteful number, since it uses less digits than its factorization.

91218993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30406334.

The product of its digits is 34992, while the sum is 42.

The square root of 91218993 is about 9550.8634688179. The cubic root of 91218993 is about 450.1546678213.

The spelling of 91218993 in words is "ninety-one million, two hundred eighteen thousand, nine hundred ninety-three".