1981851 has 4 divisors (see below), whose sum is σ = 2642472. Its totient is φ = 1321232.

The previous prime is 1981813. The next prime is 1981853. The reversal of 1981851 is 1581891.

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

It is a cyclic number.

It is not a de Polignac number, because 1981851 - 2⁶ = 1981787 is a prime.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (1981853) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 330306 + ... + 330311.

It is an arithmetic number, because the mean of its divisors is an integer number (660618).

2^1981851 is an apocalyptic number.

1981851 is a deficient number, since it is larger than the sum of its proper divisors (660621).

1981851 is an equidigital number, since it uses as much as digits as its factorization.

1981851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 660620.

The product of its digits is 2880, while the sum is 33.

The square root of 1981851 is about 1407.7822985107. The cubic root of 1981851 is about 125.6098412441.

The spelling of 1981851 in words is "one million, nine hundred eighty-one thousand, eight hundred fifty-one".