991813785 has 16 divisors (see below), whose sum is σ = 1587453504. Its totient is φ = 528783552.

The previous prime is 991813763. The next prime is 991813799. The reversal of 991813785 is 587318199.

It is not a de Polignac number, because 991813785 - 2¹⁰ = 991812761 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 40794 + ... + 60396.

It is an arithmetic number, because the mean of its divisors is an integer number (99215844).

Almost surely, 2^991813785 is an apocalyptic number.

It is an amenable number.

991813785 is a deficient number, since it is larger than the sum of its proper divisors (595639719).

991813785 is a wasteful number, since it uses less digits than its factorization.

991813785 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22984.

The product of its digits is 544320, while the sum is 51.

The square root of 991813785 is about 31493.0751912226. The cubic root of 991813785 is about 997.2637816041.

The spelling of 991813785 in words is "nine hundred ninety-one million, eight hundred thirteen thousand, seven hundred eighty-five".