1997521 has 4 divisors (see below), whose sum is σ = 2018212. Its totient is φ = 1976832.

The previous prime is 1997507. The next prime is 1997531. The reversal of 1997521 is 1257991.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1535121 + 462400 = 1239^2 + 680^2 .

It is a cyclic number.

It is not a de Polignac number, because 1997521 - 2¹¹ = 1995473 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1997531) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 10200 + ... + 10393.

It is an arithmetic number, because the mean of its divisors is an integer number (504553).

2^1997521 is an apocalyptic number.

It is an amenable number.

1997521 is a deficient number, since it is larger than the sum of its proper divisors (20691).

1997521 is an equidigital number, since it uses as much as digits as its factorization.

1997521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20690.

The product of its digits is 5670, while the sum is 34.

The square root of 1997521 is about 1413.3368317567. The cubic root of 1997521 is about 125.9400277289.

The spelling of 1997521 in words is "one million, nine hundred ninety-seven thousand, five hundred twenty-one".