991440 has 140 divisors (see below), whose sum is σ = 3659364. Its totient is φ = 248832.

The previous prime is 991429. The next prime is 991447. The reversal of 991440 is 44199.

It can be written as a sum of positive squares in 2 ways, for example, as 571536 + 419904 = 756^2 + 648^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991447) by changing a digit.

991440 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 58312 + ... + 58328.

2⁹⁹¹⁴⁴⁰ is an apocalyptic number.

991440 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 991440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1829682).

991440 is an abundant number, since it is smaller than the sum of its proper divisors (2667924).

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

991440 is a wasteful number, since it uses less digits than its factorization.

991440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48 (or 27 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 991440 is about 995.7108013876. The cubic root of 991440 is about 99.7138486216.

It can be divided in two parts, 991 and 440, that added together give a triangular number (1431 = T₅₃).

The spelling of 991440 in words is "nine hundred ninety-one thousand, four hundred forty".