91311993 has 6 divisors (see below), whose sum is σ = 131895114. Its totient is φ = 60874656.

The previous prime is 91311989. The next prime is 91312003. The reversal of 91311993 is 39911319.

It can be written as a sum of positive squares in only one way, i.e., 91240704 + 71289 = 9552^2 + 267^2 .

It is not a de Polignac number, because 91311993 - 2² = 91311989 is a prime.

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (91311193) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 5072880 + ... + 5072897.

It is an arithmetic number, because the mean of its divisors is an integer number (21982519).

Almost surely, 2^91311993 is an apocalyptic number.

It is an amenable number.

91311993 is a deficient number, since it is larger than the sum of its proper divisors (40583121).

91311993 is a wasteful number, since it uses less digits than its factorization.

91311993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10145783 (or 10145780 counting only the distinct ones).

The product of its digits is 6561, while the sum is 36.

The square root of 91311993 is about 9555.7308982620. The cubic root of 91311993 is about 450.3075971018.

The spelling of 91311993 in words is "ninety-one million, three hundred eleven thousand, nine hundred ninety-three".