1997840 has 80 divisors (see below), whose sum is σ = 5343408. Its totient is φ = 688128.

The previous prime is 1997833. The next prime is 1997843. The reversal of 1997840 is 487991.

It can be written as a sum of positive squares in 8 ways, for example, as 369664 + 1628176 = 608^2 + 1276^2 .

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 1997794 and 1997803.

It is not an unprimeable number, because it can be changed into a prime (1997843) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17624 + ... + 17736.

2^1997840 is an apocalyptic number.

1997840 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 1997840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2671704).

1997840 is an abundant number, since it is smaller than the sum of its proper divisors (3345568).

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

1997840 is a wasteful number, since it uses less digits than its factorization.

1997840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 156 (or 150 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 1997840 is about 1413.4496807457. The cubic root of 1997840 is about 125.9467314933.

The spelling of 1997840 in words is "one million, nine hundred ninety-seven thousand, eight hundred forty".