1997921 has 2 divisors, whose sum is σ = 1997922. Its totient is φ = 1997920.

The previous prime is 1997911. The next prime is 1997939. The reversal of 1997921 is 1297991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1661521 + 336400 = 1289^2 + 580^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1997921 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1997911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 998960 + 998961.

It is an arithmetic number, because the mean of its divisors is an integer number (998961).

2^1997921 is an apocalyptic number.

It is an amenable number.

1997921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1997921 is an equidigital number, since it uses as much as digits as its factorization.

1997921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10206, while the sum is 38.

The square root of 1997921 is about 1413.4783337568. The cubic root of 1997921 is about 125.9484335895.

The spelling of 1997921 in words is "one million, nine hundred ninety-seven thousand, nine hundred twenty-one".