1997851 has 2 divisors, whose sum is σ = 1997852. Its totient is φ = 1997850.

The previous prime is 1997843. The next prime is 1997867. The reversal of 1997851 is 1587991.

It is a happy number.

It is a weak prime.

It is an emirp because it is prime and its reverse (1587991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1997851 - 2³ = 1997843 is a prime.

It is not a weakly prime, because it can be changed into another prime (1997351) 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 as a sum of consecutive naturals, namely, 998925 + 998926.

It is an arithmetic number, because the mean of its divisors is an integer number (998926).

2^1997851 is an apocalyptic number.

1997851 is a deficient number, since it is larger than the sum of its proper divisors (1).

1997851 is an equidigital number, since it uses as much as digits as its factorization.

1997851 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 22680, while the sum is 40.

The square root of 1997851 is about 1413.4535719294. The cubic root of 1997851 is about 125.9469626449.

It can be divided in two parts, 19978 and 51, that multiplied together give a triangular number (1018878 = T₁₄₂₇).

The spelling of 1997851 in words is "one million, nine hundred ninety-seven thousand, eight hundred fifty-one".