91206991 has 4 divisors (see below), whose sum is σ = 94149184. Its totient is φ = 88264800.

The previous prime is 91206953. The next prime is 91207007. The reversal of 91206991 is 19960219.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 91206991 - 2¹⁹ = 90682703 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 91206991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91206491) 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, 1471050 + ... + 1471111.

It is an arithmetic number, because the mean of its divisors is an integer number (23537296).

Almost surely, 2^91206991 is an apocalyptic number.

91206991 is a deficient number, since it is larger than the sum of its proper divisors (2942193).

91206991 is a wasteful number, since it uses less digits than its factorization.

91206991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2942192.

The product of its (nonzero) digits is 8748, while the sum is 37.

The square root of 91206991 is about 9550.2351279955. The cubic root of 91206991 is about 450.1349241505.

The spelling of 91206991 in words is "ninety-one million, two hundred six thousand, nine hundred ninety-one".