991636800 has 336 divisors, whose sum is σ = 4057692672. Its totient is φ = 205977600.

The previous prime is 991636799. The next prime is 991636823. The reversal of 991636800 is 8636199.

It is a tau number, because it is divible by the number of its divisors (336).

It is a super-2 number, since 2×991636800² = 1966687086228480000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 368259 + ... + 370941.

Almost surely, 2^991636800 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 991636800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2028846336).

991636800 is an abundant number, since it is smaller than the sum of its proper divisors (3066055872).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

991636800 is a wasteful number, since it uses less digits than its factorization.

991636800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2726 (or 2711 counting only the distinct ones).

The product of its (nonzero) digits is 69984, while the sum is 42.

The square root of 991636800 is about 31490.2651624276. The cubic root of 991636800 is about 997.2044588991.

The spelling of 991636800 in words is "nine hundred ninety-one million, six hundred thirty-six thousand, eight hundred".