991383433551 has 12 divisors (see below), whose sum is σ = 1636569477712. Its totient is φ = 566504819136.

The previous prime is 991383433477. The next prime is 991383433553. The reversal of 991383433551 is 155334383199.

991383433551 is a `hidden beast` number, since 9 + 9 + 1 + 3 + 83 + 4 + 3 + 3 + 551 = 666.

It is not a de Polignac number, because 991383433551 - 2¹³ = 991383425359 is a prime.

It is a super-2 number, since 2×991383433551² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991383433553) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7868122426 + ... + 7868122551.

Almost surely, 2^991383433551 is an apocalyptic number.

991383433551 is a deficient number, since it is larger than the sum of its proper divisors (645186044161).

991383433551 is a wasteful number, since it uses less digits than its factorization.

991383433551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15736244990 (or 15736244987 counting only the distinct ones).

The product of its digits is 5248800, while the sum is 54.

The spelling of 991383433551 in words is "nine hundred ninety-one billion, three hundred eighty-three million, four hundred thirty-three thousand, five hundred fifty-one".