991910515211 has 24 divisors (see below), whose sum is σ = 1292771329776. Its totient is φ = 752027613120.

The previous prime is 991910515187. The next prime is 991910515223. The reversal of 991910515211 is 112515019199.

It is a happy number.

It is not a de Polignac number, because 991910515211 - 2⁶ = 991910515147 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991910515711) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 24848696 + ... + 24888581.

It is an arithmetic number, because the mean of its divisors is an integer number (53865472074).

Almost surely, 2^991910515211 is an apocalyptic number.

991910515211 is a deficient number, since it is larger than the sum of its proper divisors (300860814565).

991910515211 is a wasteful number, since it uses less digits than its factorization.

991910515211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49737339 (or 49737332 counting only the distinct ones).

The product of its (nonzero) digits is 36450, while the sum is 44.

The spelling of 991910515211 in words is "nine hundred ninety-one billion, nine hundred ten million, five hundred fifteen thousand, two hundred eleven".