991412640 has 144 divisors (see below), whose sum is σ = 3392782848. Its totient is φ = 263628288.

The previous prime is 991412623. The next prime is 991412663. The reversal of 991412640 is 46214199.

It is a happy number.

991412640 is a `hidden beast` number, since 9 + 9 + 1 + 4 + 1 + 2 + 640 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 991412595 and 991412604.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 665977 + ... + 667463.

It is an arithmetic number, because the mean of its divisors is an integer number (23560992).

Almost surely, 2^991412640 is an apocalyptic number.

991412640 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 991412640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1696391424).

991412640 is an abundant number, since it is smaller than the sum of its proper divisors (2401370208).

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

991412640 is a wasteful number, since it uses less digits than its factorization.

991412640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1971 (or 1960 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 991412640 is about 31486.7057660848. The cubic root of 991412640 is about 997.1293137125.

The spelling of 991412640 in words is "nine hundred ninety-one million, four hundred twelve thousand, six hundred forty".