1991658240 has 864 divisors, whose sum is σ = 8618158080. Its totient is φ = 431308800.

The previous prime is 1991658233. The next prime is 1991658241. The reversal of 1991658240 is 428561991.

1991658240 is a `hidden beast` number, since 19 + 9 + 16 + 582 + 40 = 666.

It is a tau number, because it is divible by the number of its divisors (864).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991658241) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 64247025 + ... + 64247055.

It is an arithmetic number, because the mean of its divisors is an integer number (9974720).

Almost surely, 2^1991658240 is an apocalyptic number.

1991658240 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 1991658240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (4309079040).

1991658240 is an abundant number, since it is smaller than the sum of its proper divisors (6626499840).

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

1991658240 is a wasteful number, since it uses less digits than its factorization.

1991658240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98 (or 65 counting only the distinct ones).

The product of its (nonzero) digits is 155520, while the sum is 45.

The square root of 1991658240 is about 44627.9983866631. The cubic root of 1991658240 is about 1258.1669490789.

The spelling of 1991658240 in words is "one billion, nine hundred ninety-one million, six hundred fifty-eight thousand, two hundred forty".