815191993 has 16 divisors (see below), whose sum is σ = 1035524736. Its totient is φ = 623226240.

The previous prime is 815191991. The next prime is 815191997. The reversal of 815191993 is 399191518.

It is not a de Polignac number, because 815191993 - 2¹ = 815191991 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (815191991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 95796 + ... + 103957.

It is an arithmetic number, because the mean of its divisors is an integer number (64720296).

Almost surely, 2^815191993 is an apocalyptic number.

It is an amenable number.

815191993 is a deficient number, since it is larger than the sum of its proper divisors (220332743).

815191993 is a wasteful number, since it uses less digits than its factorization.

815191993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 199824.

The product of its digits is 87480, while the sum is 46.

The square root of 815191993 is about 28551.5672599597. The cubic root of 815191993 is about 934.1572063653.

The spelling of 815191993 in words is "eight hundred fifteen million, one hundred ninety-one thousand, nine hundred ninety-three".