1991485440 has 600 divisors, whose sum is σ = 8327288970. Its totient is φ = 455196672.

The previous prime is 1991485423. The next prime is 1991485453. The reversal of 1991485440 is 445841991.

It is a happy number.

1991485440 is a `hidden beast` number, since 1 + 99 + 14 + 8 + 544 + 0 = 666.

It can be written as a sum of positive squares in only one way, i.e., 1792336896 + 199148544 = 42336^2 + 14112^2 .

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 49 ways as a sum of consecutive naturals, for example, 284497917 + ... + 284497923.

Almost surely, 2^1991485440 is an apocalyptic number.

1991485440 is a gapful number since it is divisible by the number (10) 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 1991485440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (4163644485).

1991485440 is an abundant number, since it is smaller than the sum of its proper divisors (6335803530).

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

1991485440 is an frugal number, since it uses more digits than its factorization.

1991485440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67 (or 17 counting only the distinct ones).

The product of its (nonzero) digits is 207360, while the sum is 45.

The square root of 1991485440 is about 44626.0623402962. The cubic root of 1991485440 is about 1258.1305610527.

Multiplying 1991485440 by its product of nonzero digits (207360), we get a square (412954420838400 = 20321280²).

1991485440 divided by its product of nonzero digits (207360) gives a square (9604 = 98²).

The spelling of 1991485440 in words is "one billion, nine hundred ninety-one million, four hundred eighty-five thousand, four hundred forty".