1997640 has 96 divisors (see below), whose sum is σ = 6739200. Its totient is φ = 512640.

The previous prime is 1997617. The next prime is 1997647. The reversal of 1997640 is 467991.

1997640 is a `hidden beast` number, since 1 + 9 + 9 + 7 + 640 = 666.

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

It is a zygodrome in base 7.

It is a junction number, because it is equal to n+sod(n) for n = 1997595 and 1997604.

It is not an unprimeable number, because it can be changed into a prime (1997647) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11071 + ... + 11249.

It is an arithmetic number, because the mean of its divisors is an integer number (70200).

2^1997640 is an apocalyptic number.

1997640 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 1997640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3369600).

1997640 is an abundant number, since it is smaller than the sum of its proper divisors (4741560).

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

1997640 is a wasteful number, since it uses less digits than its factorization.

1997640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 227 (or 220 counting only the distinct ones).

The product of its (nonzero) digits is 13608, while the sum is 36.

The square root of 1997640 is about 1413.3789300821. The cubic root of 1997640 is about 125.9425285897.

The spelling of 1997640 in words is "one million, nine hundred ninety-seven thousand, six hundred forty".