991951911 has 12 divisors (see below), whose sum is σ = 1433097120. Its totient is φ = 661173120.

The previous prime is 991951901. The next prime is 991951957. The reversal of 991951911 is 119159199.

It is not a de Polignac number, because 991951911 - 2⁵ = 991951879 is a prime.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991951901) by changing a digit.

It is an upside-down number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 72151 + ... + 84791.

It is an arithmetic number, because the mean of its divisors is an integer number (119424760).

Almost surely, 2^991951911 is an apocalyptic number.

991951911 is a deficient number, since it is larger than the sum of its proper divisors (441145209).

991951911 is a wasteful number, since it uses less digits than its factorization.

991951911 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21366 (or 21363 counting only the distinct ones).

The product of its digits is 32805, while the sum is 45.

The square root of 991951911 is about 31495.2680731566. The cubic root of 991951911 is about 997.3100744551.

The spelling of 991951911 in words is "nine hundred ninety-one million, nine hundred fifty-one thousand, nine hundred eleven".